chore: CI worfklows for linting docs

[maxrjones]

This PR adds a few scripts/workflows to:

• Check that all top-level functions are included in the mkdocs API documentation
• Check that docstrings use mkdocs rather than sphinx styles admonitions and links
• Check that all links resolve

TODO:

• Add unit tests and/or doctests in docstrings
• Add docstrings and API docs for any new/modified user-facing classes and functions
• New/modified features documented in docs/user-guide/*.md
• Changes documented as a new file in changes/
• GitHub Actions have all passed
• Test coverage is 100% (Codecov passes)

[maxrjones]

@d-v-b @chuckwondo this adds a fair amount of config/workflow files, so a review on the direction here would be welcome but not necessarily required

[maxrjones]

thanks for the review @chuckwondo. I applied your fixes in fd36246 (this PR) and some other readability improvements. I chose to make the directory an optional argument.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.50%. Comparing base (fd6189b) to head (ce89d7f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4076   +/-   ##
=======================================
  Coverage   93.50%   93.50%           
=======================================
  Files          90       90           
  Lines       11979    11979           
=======================================
  Hits        11201    11201           
  Misses        778      778           

Files with missing lines	Coverage Δ
src/zarr/core/metadata/v2.py	89.44% <ø> (ø)
src/zarr/testing/store.py	99.43% <ø> (ø)

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