Add linkcheck to CI

[anissa111]

This PR:

• adds a linkcheck to CI
  • adds linkcheck.yml as a separate action workflow file so that our entire CI won't show as failing if just linkcheck is having problems and potential linkcheck problems won't necessarily block PRs.
  • runs on main at 00:30 UTC, on PRs, and on workflow call
  • reuses the environment generated by nightly checks (hence running at 00:30 UTC)
• and addresses some stuff that made it fail
  • adds :ref: roles to internal links in cards in applications/applications.rst and index.rst
  • alters references.bib to remove redundant urls and correct a typo in a doi
  • adds linkcheck_anchors = False to conf.py to allow linking to specific line numbers on github (invalid anchors will still go to the intended page, just not the intended location)
  • adds linkcheck_ignore = [r'https://doi.org/10.1080/104732299303296'] to conf.py. I tried to do some stuff with the user agent, but ultimately, this page is really interested in keeping track of the number of people who access it and I don't want to mess with their stats.

Addresses GA-1499

[github-actions]

Meowdy! See your PR preview:
🔍 Git commit SHA: 6668352
✅ Deployment Preview URL: https://NCAR.github.io/geocat-applications/_preview/141

[anissa111]

Task linked: GA-1499 Add link checker to geocat-applications

[cyschneck]

Looks good, might be worth updating the Contributor guide to mention some of the link details like using ref

[kafitzgerald]

Looks great!

Unreasonably excited to have this 😆