Fix the things that broke when we renamed master -> main

[kandersolar]

• Closes #xxxx
• I am familiar with the contributing guidelines
• Tests added
• Updates entries in docs/sphinx/source/reference for API changes.
• Adds description and name entries in the appropriate "what's new" file in docs/sphinx/source/whatsnew for all changes. Includes link to the GitHub Issue with :issue:`num` or this Pull Request with :pull:`num`. Includes contributor name and/or GitHub username (link with :ghuser:`user`).
• New code is fully documented. Includes numpydoc compliant docstrings, examples, and comments where necessary.
• Pull request is nearly complete and ready for detailed review.
• Maintainer: Appropriate GitHub Labels (including remote-data) and Milestone are assigned to the Pull Request and linked Issue.

I just noticed that the CI hasn't been running on main for the last several commits, likely because of renaming our primary branch but not updating the CI configs. We also have a ton of broken links scattered through the docs. This PR goes through and updates all those things.

[AdamRJensen]

I did a fairly extensive search for "master" and all your changes checks out.

[wholmgren]

@kanderso-nrel merge it?

[kandersolar]

Thanks folks!