Added and updated droplab docs

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diff --git a/doc/development/fe_guide/droplab/droplab.md b/doc/development/fe_guide/droplab/droplab.md
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+# DropLab
+
+A generic dropdown for all of your custom dropdown needs.
+
+## Usage
+
+DropLab can be used by simply adding a `data-dropdown-trigger` HTML attribute.
+This attribute allows us to find the "trigger" _(toggle)_ for the dropdown,
+whether that is a button, link or input.
+
+The value of the `data-dropdown-trigger` should be a CSS selector that
+DropLab can use to find the trigger's dropdown list.
+
+You should also add the `data-dropdown` attribute to declare the dropdown list.
+The value is irrelevant.
+
+The DropLab class has no side effects, so you must always call `.init` when
+the DOM is ready. `DropLab.prototype.init` takes the same arguments as `DropLab.prototype.addHook`.
+If you do not provide any arguments, it will globally query and instantiate all droplab compatible dropdowns.
+
+```html
+<a href="#" data-dropdown-trigger="#list">Toggle</a>
+
+<ul id="list" data-dropdown>
+  <!-- ... -->
+<ul>
+```
+```js
+const droplab = new DropLab();
+droplab.init();
+```
+
+As you can see, we have a "Toggle" link, that is declared as a trigger.
+It provides a selector to find the dropdown list it should control.
+
+### Static data
+
+You can add static list items.
+
+```html
+<a href="#" data-dropdown-trigger="#list">Toggle</a>
+
+<ul id="list" data-dropdown>
+  <li>Static value 1</li>
+  <li>Static value 2</li>
+<ul>
+```
+```js
+const droplab = new DropLab();
+droplab.init();
+```
+
+### Explicit instantiation
+
+You can pass the trigger and list elements as constructor arguments to return
+a non-global instance of DropLab using the `DropLab.prototype.init` method.
+
+```html
+<a href="#" id="trigger" data-dropdown-trigger="#list">Toggle</a>
+
+<ul id="list" data-dropdown>
+  <!-- ... -->
+<ul>
+```
+```js
+const trigger = document.getElementById('trigger');
+const list = document.getElementById('list');
+
+const droplab = new DropLab();
+droplab.init(trigger, list);
+```
+
+You can also add hooks to an existing DropLab instance using `DropLab.prototype.addHook`.
+
+```html
+<a href="#" data-dropdown-trigger="#auto-dropdown">Toggle</a>
+<ul id="auto-dropdown" data-dropdown><!-- ... --><ul>
+
+<a href="#" id="trigger" data-dropdown-trigger="#list">Toggle</a>
+<ul id="list" data-dropdown><!-- ... --><ul>
+```
+```js
+const droplab = new DropLab();
+
+droplab.init();
+
+const trigger = document.getElementById('trigger');
+const list = document.getElementById('list');
+
+droplab.addHook(trigger, list);
+```
+
+
+### Dynamic data
+
+Adding `data-dynamic` to your dropdown element will enable dynamic list rendering.
+
+You can template a list item using the keys of the data object provided.
+Use the handlebars syntax `{{ value }}` to HTML escape the value.
+Use the `<%= value %>` syntax to simply interpolate the value.
+Use the `<%= value %>` syntax to evaluate the value.
+
+Passing an array of objects to `DropLab.prototype.addData` will render that data
+for all `data-dynamic` dropdown lists tracked by that DropLab instance.
+
+```html
+<a href="#" data-dropdown-trigger="#list">Toggle</a>
+
+<ul id="list" data-dropdown data-dynamic>
+  <li><a href="#" data-id="{{id}}">{{text}}</a></li>
+</ul>
+```
+```js
+const droplab = new DropLab();
+
+droplab.init().addData([{
+  id: 0,
+  text: 'Jacob',
+}, {
+  id: 1,
+  text: 'Jeff',
+}]);
+```
+
+Alternatively, you can specify a specific dropdown to add this data to but passing
+the data as the second argument and and the `id` of the trigger element as the first argument.
+
+```html
+<a href="#" data-dropdown-trigger="#list" id="trigger">Toggle</a>
+
+<ul id="list" data-dropdown data-dynamic>
+  <li><a href="#" data-id="{{id}}">{{text}}</a></li>
+</ul>
+```
+```js
+const droplab = new DropLab();
+
+droplab.init().addData('trigger', [{
+  id: 0,
+  text: 'Jacob',
+}, {
+  id: 1,
+  text: 'Jeff',
+}]);
+```
+
+This allows you to mix static and dynamic content with ease, even with one trigger.
+
+Note the use of scoping regarding the `data-dropdown` attribute to capture both
+dropdown lists, one of which is dynamic.
+
+```html
+<input id="trigger" data-dropdown-trigger="#list">
+<div id="list" data-dropdown>
+  <ul>
+    <li><a href="#">Static item 1</a></li>
+    <li><a href="#">Static item 2</a></li>
+  </ul>
+  <ul data-dynamic>
+    <li><a href="#" data-id="{{id}}">{{text}}</a></li>
+  </ul>
+</div>
+```
+```js
+const droplab = new DropLab();
+
+droplab.init().addData('trigger', [{
+  id: 0,
+  text: 'Jacob',
+}, {
+  id: 1,
+  text: 'Jeff',
+}]);
+```
+
+## Internal selectors
+
+DropLab adds some CSS classes to help lower the barrier to integration.
+
+For example,
+
+* The `droplab-item-selected` css class is added to items that have been selected
+either by a mouse click or by enter key selection.
+* The `droplab-item-active` css class is added to items that have been selected
+using arrow key navigation.
+
+## Internal events
+
+DropLab uses some custom events to help lower the barrier to integration.
+
+For example,
+
+* The `click.dl` event is fired when an `li` list item has been clicked. It is also
+fired when a list item has been selected with the keyboard. It is also fired when a
+`HookButton` button is clicked (a registered `button` tag or `a` tag trigger).
+* The `input.dl` event is fired when a `HookInput` (a registered `input` tag trigger) triggers an `input` event.
+* The `mousedown.dl` event is fired when a `HookInput` triggers a `mousedown` event.
+* The `keyup.dl` event is fired when a `HookInput` triggers a `keyup` event.
+* The `keydown.dl` event is fired when a `HookInput` triggers a `keydown` event.
+
+These custom events add a `detail` object to the vanilla `Event` object that provides some potentially useful data.
+
+## Plugins
+
+Plugins are objects that are registered to be executed when a hook is added (when a droplab trigger and dropdown are instantiated).
+
+If no modules API is detected, the library will fall back as it does with `window.DropLab` and will add `window.DropLab.plugins.PluginName`.
+
+### Usage
+
+To use plugins, you can pass them in an array as the third argument of `DropLab.prototype.init` or `DropLab.prototype.addHook`.
+Some plugins require configuration values, the config object can be passed as the fourth argument.
+
+```html
+<a href="#" id="trigger" data-dropdown-trigger="#list">Toggle</a>
+<ul id="list" data-dropdown><!-- ... --><ul>
+```
+```js
+const droplab = new DropLab();
+
+const trigger = document.getElementById('trigger');
+const list = document.getElementById('list');
+
+droplab.init(trigger, list, [droplabAjax], {
+  droplabAjax: {
+    endpoint: '/some-endpoint',
+    method: 'setData',
+  },
+});
+```
+
+### Documentation
+
+* [Ajax plugin](plugins/ajax.md)
+* [Filter plugin](plugins/filter.md)
+* [InputSetter plugin](plugins/input_setter.md)
+
+### Development
+
+When plugins are initialised for a droplab trigger+dropdown, DropLab will
+call the plugins `init` function, so this must be implemented in the plugin.
+
+```js
+class MyPlugin {
+  static init() {
+    this.someProp = 'someProp';
+    this.someMethod();
+  }
+
+  static someMethod() {
+    this.otherProp = 'otherProp';
+  }
+}
+
+export default MyPlugin;
+```
diff --git a/doc/development/fe_guide/droplab/plugins/ajax.md b/doc/development/fe_guide/droplab/plugins/ajax.md
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+# Ajax
+
+`Ajax` is a droplab plugin that allows for retrieving and rendering list data from a server.
+
+## Usage
+
+Add the `Ajax` object to the plugins array of a `DropLab.prototype.init` or `DropLab.prototype.addHook` call.
+
+`Ajax` requires 2 config values, the `endpoint` and `method`.
+
+* `endpoint` should be a URL to the request endpoint.
+* `method` should be `setData` or `addData`.
+* `setData` completely replaces the dropdown with the response data.
+* `addData` appends the response data to the current dropdown list.
+
+```html
+<a href="#" id="trigger" data-dropdown-trigger="#list">Toggle</a>
+<ul id="list" data-dropdown><!-- ... --><ul>
+```
+```js
+  const droplab = new DropLab();
+
+  const trigger = document.getElementById('trigger');
+  const list = document.getElementById('list');
+
+  droplab.addHook(trigger, list, [Ajax], {
+    Ajax: {
+      endpoint: '/some-endpoint',
+      method: 'setData',
+    },
+  });
+```
+
+Optionally you can set `loadingTemplate` to a HTML string. This HTML string will
+replace the dropdown list whilst the request is pending.
+
+Additionally, you can set `onError` to a function to catch any XHR errors.
diff --git a/doc/development/fe_guide/droplab/plugins/filter.md b/doc/development/fe_guide/droplab/plugins/filter.md
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+# Filter
+
+`Filter` is a plugin that allows for filtering data that has been added
+to the dropdown using a simple fuzzy string search of an input value.
+
+## Usage
+
+Add the `Filter` object to the plugins array of a `DropLab.prototype.init` or `DropLab.prototype.addHook` call.
+
+* `Filter` requires a config value for `template`.
+* `template` should be the key of the objects within your data array that you want to compare
+to the user input string, for filtering.
+
+```html
+<input href="#" id="trigger" data-dropdown-trigger="#list">
+<ul id="list" data-dropdown data-dynamic>
+  <li><a href="#" data-id="{{id}}">{{text}}</a></li>
+<ul>
+```
+```js
+  const droplab = new DropLab();
+
+  const trigger = document.getElementById('trigger');
+  const list = document.getElementById('list');
+
+  droplab.init(trigger, list, [Filter], {
+    Filter: {
+      template: 'text',
+    },
+  });
+
+  droplab.addData('trigger', [{
+    id: 0,
+    text: 'Jacob',
+  }, {
+    id: 1,
+    text: 'Jeff',
+  }]);
+```
+
+Above, the input string will be compared against the `test` key of the passed data objects.
+
+Optionally you can set `filterFunction` to a function. This function will be used instead
+of `Filter`'s built in string search. `filterFunction` is passed 2 arguments, the first
+is one of the data objects, the second is the current input value.
diff --git a/doc/development/fe_guide/droplab/plugins/input_setter.md b/doc/development/fe_guide/droplab/plugins/input_setter.md
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+# InputSetter
+
+`InputSetter` is a plugin that allows for udating DOM out of the scope of droplab when a list item is clicked.
+
+## Usage
+
+Add the `InputSetter` object to the plugins array of a `DropLab.prototype.init` or `DropLab.prototype.addHook` call.
+
+* `InputSetter` requires a config value for `input` and `valueAttribute`.
+* `input` should be the DOM element that you want to manipulate.
+* `valueAttribute` should be a string that is the name of an attribute on your list items that is used to get the value
+to update the `input` element with.
+
+You can also set the `InputSetter` config to an array of objects, which will allow you to update multiple elements.
+
+
+```html
+<input id="input" value="">
+<div id="div" data-selected-id=""></div>
+
+<input href="#" id="trigger" data-dropdown-trigger="#list">
+<ul id="list" data-dropdown data-dynamic>
+  <li><a href="#" data-id="{{id}}">{{text}}</a></li>
+<ul>
+```
+```js
+  const droplab = new DropLab();
+
+  const trigger = document.getElementById('trigger');
+  const list = document.getElementById('list');
+
+  const input = document.getElementById('input');
+  const div = document.getElementById('div');
+
+  droplab.init(trigger, list, [InputSetter], {
+    InputSetter: [{
+      input: input,
+      valueAttribute: 'data-id',
+    } {
+      input: div,
+      valueAttribute: 'data-id',
+      inputAttribute: 'data-selected-id',
+    }],
+  });
+
+  droplab.addData('trigger', [{
+    id: 0,
+    text: 'Jacob',
+  }, {
+    id: 1,
+    text: 'Jeff',
+  }]);
+```
+
+Above, if the second list item was clicked, it would update the `#input` element
+to have a `value` of `1`, it would also update the `#div` element's `data-selected-id` to `1`.
+
+Optionally you can set `inputAttribute` to a string that is the name of an attribute on your `input` element that you want to update.
+If you do not provide an `inputAttribute`, `InputSetter` will update the `value` of the `input` element if it is an `INPUT` element,
+or the `textContent` of the `input` element if it is not an `INPUT` element.
diff --git a/doc/development/fe_guide/index.md b/doc/development/fe_guide/index.md
index f963bffde37..c7d4f2e9c23 100644
--- a/doc/development/fe_guide/index.md
+++ b/doc/development/fe_guide/index.md
@@ -90,3 +90,13 @@ Our accessibility standards and resources.
 [scss-lint]: https://github.com/brigade/scss-lint
 [install]: ../../install/installation.md#4-node
 [requirements]: ../../install/requirements.md#supported-web-browsers
+
+---
+
+## [DropLab](droplab/droplab.md)
+Our internal `DropLab` dropdown library.
+
+* [DropLab](droplab/droplab.md)
+* [Ajax plugin](droplab/plugins/ajax.md)
+* [Filter plugin](droplab/plugins/filter.md)
+* [InputSetter plugin](droplab/plugins/input_setter.md)