Add reference to complementary Click CLI documentation helpers

[kdeldycke]

Summary

As suggested by @stephenfin at https://github.com/click-contrib/sphinx-click/issues/110#issuecomment-1208039848, here is a little update to point users to complementary tools to help them document their Click-based CLI.

This PR also fixes some rST style rendering in the README.rst.

Tasks

• [x] Added unit tests
• [x] Added documentation for new features (where applicable)
• [x] Added release notes (using reno)
• [x] Ran test suite and style checks and built documentation (tox)

Further details

Here are some examples of real projects using click-extra's .. click:run:: to render the output of their --help option, followed by the rendering of .. click:: directive from sphinx-click extension:

• Meta Package Manager
• Mail Deduplicate

[kdeldycke]

Thanks @stephenfin for the fast merge!

[kdeldycke]

And sorry, I just realized there's a tiny typo. Made a PR to fix that at https://github.com/click-contrib/sphinx-click/pull/118