Add automated tests

[JWCook]

Closes #38

Test setup

• Added structure for a test suite using the sphinx.testing plugin
  • I added some notes in conftest.py on how the tests are set up, but let me know if any of that doesn't make sense.
  • I think the least obvious part is how input directories are passed to SphinxTestApp (via a pytest fixture and a marker). That's how Sphinx's own tests do it, but it seems potentially confusing.
• Run tests in CircleCI
• A test coverage report is generated in the CI job and also output to the console.
  • If you wanted to, you could send this coverage report to Codecov (or a similar site) and enable PR integration
  • You could also add a coverage badge to your readme if you'd like, and show off your shiny new 98% coverage :)

Coverage

Test coverage has been added for:

• Tags with emoji, spaces, and other special characters
• Tags in subdirectories
• Symlinked files and directories
• Jupyter notebooks
• Tagged pages (text output of tags directive)
• Badges
  • Badge colors
• Sources excluded by exclude_patterns

[JWCook]

@melissawm I believe this PR is ready to go. This depends on merging #57 first, so once that's done I can rebase this one.

[JWCook]

I rebased this on top of main, so this is ready to go.

[melissawm]

Running pytest on this with Python 3.12, Sphinx 7.2.6, pytest 7.4.3 I get

  /home/melissa/projects/sphinx-tags/test/conftest.py:18: RemovedInSphinx90Warning: 'sphinx.testing.path' is deprecated. Use 'os.path' or 'pathlib' instead.

This is not a blocker though - we could put this in and deal with the deprecation later.

[JWCook]

Hmm, I originally tried pathlib, but using sphinx.testing.path seemed to be required for Sphinx<=6. You can create another issue for that if you want, and I can look into it some more later.

[melissawm]

I'm not going to say I understand all details but I do get the overall idea and I see zero reasons to hold this off - thank you so much for being patient and sticking with it! I have a few more details to sort and should be cutting a release later this weekend. Cheers!