[develop]: Add GitHub Actions to check that Technical Docs are up-to-date

[gspetro-NOAA]

DESCRIPTION OF CHANGES:

This PR:

• Adds a GitHub Actions workflow & script to check whether the Technical Documentation is up-to-date
• Turns on the -W flag so that documentation build warnings register as error
• Updates the requirements file so that --remove-old flag can be used to check Tech Docs
• Updates the Contributor's Guide w/information on Technical Documentation and troubleshooting guidelines
• Fixes a few broken links.

Type of change

• New feature (non-breaking change which adds functionality)

TESTS CONDUCTED:

Ran fundamental tests on Hera & Hercules. All passed.
I also tested the GitHub Actions functionality by adding or deleting test files and checking that the GitHub Actions behavior (pass/fail) corresponded to the expected behavior.

• derecho.intel
• gaea.intel
• hera.gnu
• hera.intel
• hercules.intel
• jet.intel
• orion.intel
• wcoss2.intel
• NOAA Cloud (indicate which platform)
• Jenkins
• fundamental test suite
• comprehensive tests (specify which if a subset was used)

DEPENDENCIES:

N/A

DOCUMENTATION:

Documentation was added to the Contributor's Guide to explain technical documentation standards.

ISSUE:

Closes Issue #1151

CHECKLIST

• My code follows the style guidelines in the Contributor's Guide
• I have performed a self-review of my own code using the Code Reviewer's Guide
• I have commented my code, particularly in hard-to-understand areas
• My changes need updates to the documentation. I have made corresponding changes to the documentation
• My changes do not require updates to the documentation (explain). N/A
• My changes generate no new warnings
• New and existing tests pass with my changes
• Any dependent changes have been merged and published N/A

CONTRIBUTORS (optional):

[MichaelLueken]

@gspetro-NOAA -

The changes look good to me! I would suggest removing the feature/doc-actions branch from the workflow_dispatch in .github/workflows/doc_tests.yaml, since this feature branch won't require manual submission of the GHA once this PR is merged.

[rickgrubin-noaa]

LGTM -- approved pending change (removal of github action) asked for by @MichaelLueken.