Documentation updates (`CONTIBUTING.md` link, redirector, and local build guidance)

[d33bs]

Description

This PR fixes the CONTRIBUTING.md link so it properly links to always-available documentation, adds to the redirector in case the main branch is not readable (when there are no additional commits beyond the current release tag), and adds local build guidance. Normally these could each be a separate PR but they were tiny and felt cohesive in the sense that they all pertain to docs.

Thanks for any feedback!

Closes #107 Closes #97 Closes #92

What kind of change(s) are included?

• [x] Documentation (changes docs or other related content)
• [x] Bug fix (fixes an issue).
• [ ] Enhancement (adds functionality).
• [ ] Breaking change (these changes would cause existing functionality to not work as expected).

Checklist

Please ensure that all boxes are checked before indicating that this pull request is ready for review.

• [x] I have read and followed the CONTRIBUTING.md guidelines.
• [x] I have searched for existing content to ensure this is not a duplicate.
• [x] I have performed a self-review of these additions (including spelling, grammar, and related).
• [x] These changes pass all pre-commit checks.
• [x] I have added comments to my code to help provide understanding
• [ ] I have added a test which covers the code changes found within this PR
• [x] I have deleted all non-relevant text in this pull request template.

[d33bs]

Thanks @jenna-tomkinson ! Merging this in now.