chore: add dbt-coverage report

[Ian2012]

Description

This PR modifies the documentation workflow to add a check with documentation coverage. Eventually, it can be modified to verify test coverage.

This PR also adds documentation for every dataset.

[openedx-webhooks]

Thanks for the pull request, @Ian2012! Please note that it may take us up to several weeks or months to complete a review and merge your PR.

Feel free to add as much of the following information to the ticket as you can:

• supporting documentation
• Open edX discussion forum threads
• timeline information ("this must be merged by XX date", and why that is)
• partner information ("this is a course on edx.org")
• any other information that can help Product understand the context for the PR

All technical communication about the code itself will be done via the GitHub pull request interface. As a reminder, our process documentation is here.

Please let us know once your PR is ready for our review and all tests are green.

[bmtcril]

I think maybe coverage.json should be added to .gitignore? I know for other coverage things it's an artifact file that gets generated as part of the run but isn't kept around between runs.

[openedx-webhooks]

@Ian2012 🎉 Your pull request was merged! Please take a moment to answer a two question survey so we can improve your experience in the future.