By default autodocs only show class docstrings and hide __init__
https://www.sphinx-doc.org/en/master/usage/extensions/autodoc.html#confval-autoclass_content
https://www.sphinx-doc.org/en/master/usage/extensions/autodoc.html#confval-autodoc_default_options

Make sure docstrings added to __init__ functions show up in the docs

* autodoc wasn't generating docs correnctly
* add pytest so sphinx can render test docs, excluding them from docs
  for now though (so generated, but no link to them)
* Update version info in docs/conf.py
* Fix a few sphinx warnings
* Add in changelog into docs and switch to toctree depth of 1, as the
  changelog has a lat of H2 headers.
* Add docs to CI

https://black.readthedocs.io/en/stable/index.html

When defining `long_description` in setup.cfg using the `file:`
directive, we need to keep everything on one line. Otherwise, it will
treat the value as a block of literal text.