Add MyST-Parser and link community files in docs sidebar

[julianz-]

Add myst-parser to docs dependencies and Sphinx extensions, enabling Markdown support. Link the Code of Conduct and License in the docs sidebar as an initial test of the integration.

❓ What kind of change does this PR introduce?

• 🐞 bug fix
• 🐣 feature
• 📋 docs update
• 📋 tests/coverage improvement
• 📋 refactoring
• 💥 other

📋 What is the related issue number (starting with #)

Resolves #

❓ What is the current behavior? (You can also link to an open issue here)

❓ What is the new behavior (if this is a feature change)?

📋 Other information:

📋 Contribution checklist:

(If you're a first-timer, check out
[this guide on making great pull requests][making a lovely PR])

• I wrote descriptive pull request text above
• I think the code is well written
• I wrote [good commit messages]
• I have [squashed related commits together][related squash] after
  the changes have been approved
• Unit tests for the changes exist
• Integration tests for the changes exist (if applicable)
• I used the same coding conventions as the rest of the project
• The new code doesn't generate linter offenses
• Documentation reflects the changes
• The PR relates to only one subject with a clear title
  and description in grammatically correct, complete sentences

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.77%. Comparing base (3937fe1) to head (4d6933a).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #835      +/-   ##
==========================================
- Coverage   78.19%   77.77%   -0.42%     
==========================================
  Files          41       41              
  Lines        4788     4788              
  Branches      547      547              
==========================================
- Hits         3744     3724      -20     
- Misses        905      922      +17     
- Partials      139      142       +3     

[webknjaz]

Need to decide how to deal w/ https://github.com/cherrypy/cheroot/actions/runs/28755500504/job/85261942391#step:16:82. I think where were a few toggles in the Sphinx config. One way could be cutting the doc on inclusion. I'd need to check how I used to handle this in other places but if you want to look, the solution is probably in one of sphinx-contrib/towncrier, ansible/pylibssh, ansible/awx-plugins or jazzband/pip-tools.

[webknjaz]

For the future: modern versions of Sphinx can do this natively, we should try to migrate some day.

[webknjaz]

I think sphinx-issues provides a :pypi: role. Let's try it out:

Suggested change

	Added ``myst-parser`` to enable Markdown support in Sphinx documentation,
	Added :pypi:`myst-parser` to enable Markdown support in Sphinx documentation,

[webknjaz]

We could also reference said docs via relevant Sphinx roles.

[webknjaz]

Instead of putting these on the top-level, have the docs under the contrib dir. Just like the guidelines above.

[webknjaz]

Also, no need to add explicit titles in two places if they don't differ.

[webknjaz]

This breaks the docs build: https://app.readthedocs.org/projects/cheroot/builds/33450467/#328554371--132. There's even not PR preview because the build doesn't complete.

[webknjaz]

Is this a symlink? No need to do this. Use the Sphinx-native include role like https://github.com/ansible/pylibssh/blob/0efb3df9a8f1a32ba7ac0c4ee073b950481e0527/docs/contributing/code_of_conduct.rst?plain=1#L1 / https://github.com/ansible/awx-plugins/blob/7c6a7cf97ec1e2ed3c36c0dd2e0dbb29436dea78/docs/contributing/code_of_conduct.md?plain=1#L1

[webknjaz]

I've started annotating the direct dep additions w/ their purpose in other projects

Suggested change

	myst-parser
	myst-parser[linkify] # Markdown documents support w/ in-text link detector

[webknjaz]

Suggested change

	'myst_parser',
	'myst_parser', # extended markdown; https://pypi.org/p/myst-parser

[webknjaz]

I'm not entirely sure we should be rendering the license text in the docs. A lot of projects just have it in the packaging metadata + GH. But if you fix the build, we could see how it renders, I suppose.
Otherwise, I'd just postpone. Having CoC included should be enough to test how MyST-Parser integrates and would give us the build infra for adding more Markdown separately w/o having to think about the configuration bits.

[webknjaz]

Let's not include this change. I think we should be able to get rid of the docs extra here as it's an ancient leftover. Try doing so in a separate PR to see if anything depends on this docs extra.

[webknjaz]

I think #828 should be completed first to reduce the amount of noise in CI as it's difficult to sort through the unrelated failures otherwise.