Also fixes instances in Markdown that broke the rule.

Fixing square brackets, links, etc in:
  merge_requests.md
  vulnerabilities.md
  issues.md
  issues_statistics.md
  pipelines.md
  services.md
  group_milestones.md
  milestones.md
  runners.md
  changelog.md
  issue_workflow.md
  elasticsearch.md
  api_graphql_styleguide.md
  automatic_ce_ee_merge.md
  file_storage.md
  architecture.md
  database_debugging.md
  index.md
  index.md
  frontend_testing.md
  pry_debugging.md
  vue.md
  development_process.md

Linting rule not enabled for now
because tooling produces false
positives.

Add links to useful browser extensions and learning resources to the
FE-accessibility documentation.

This copy button manages a local instance of the Clipboard plugin
specific to it, which means it is created/destroyed on the
creation/destruction of the component. This allows it to work well in
gitlab-ui modals, as the event listeners are bound on creation of the
button.

It also allows for bindings to the `container` option of the Clipboard
plugin, which allows it to work within the focus trap set by bootstrap's
modals.