Add Nox setup & setup-remotes commands + other improvements

[CAM-Gerlach]

Pull Request

Pull Request Checklist

• Read and followed this repo's Contributing Guidelines
• Based your PR on the latest version of the correct branch (master or 4.x)
• Checked your writing carefully for correct English spelling, grammar, etc
• Described your changes and the motivation for them below

Description of Changes

The new setup-remotes action not only sets up the origin and upstream remotes in both the recommended fetch and push configuration by connection method (HTTPS or SSH), but also detects and offers to fix issues with the existing config.

• Implement final improvements and fixes to Nox infra
  • Add setup Nox action to set up upstream remote (and fetch), install hooks and clean build dir
  • Add setup action to Contributing Guide
  • Add docs alias for build commands (and also change _docs)
  • Also change run to error if no args passed
  • Check for and fix other issues

[CAM-Gerlach]

Linkcheck errors are due to the missing installers for Mac and Linux at present, and due to the Binder site being apparently completely down. Given there's not a strong urgency to merge this immediately, hopefully both are fixed tomorrow.

They are, I would presume, broken on our website too. It does beg the question of whether we should wait to publish the GitHub release until we know all the installers are built and ready to be uploaded, to avoid breaking everything. I thought we'd agreed to do something like that, but I guess maybe not? Or at least we could mark it as a pre-release until everything is ready, assuming that can be changed post facto?

[ccordoba12]

Just a single suggestion for you @CAM-Gerlach, the rest looks good to me.

[ccordoba12]

Thanks @CAM-Gerlach!