MAINT: Clean and update documentation

[HaoZeke]

Closes #1427 and re-hauls the documentation for the new release. For the new release.

[mattip]

This is a very large PR, I will find it hard to review. Is there something in particular you would like me to look at?

[HaoZeke]

This is a very large PR, I will find it hard to review. Is there something in particular you would like me to look at?

Ah sorry, I'll highlight a few places, in general there aren't too many differences, mostly cosmetic / documentation changes, that is:

• Uses bibtex for references, adds a logo (light/dark) and switched to furo
• Removed the spurious makefile stuff (which accounts for most of the deletions)
• Moved long module documentation (step detection) into its own page
• Uses AutoAPI and viewcode for more through documentation
  • This also means the sphinx build doesn't import asv anymore
  • Uses importlib_metadata to consistently get the version as suggested by setuptools_scm

Here is what the documentation looks like at this commit, e88a2ac:
https://tmpasv.surge.sh/

[mattip]

It all seems quite straightforward, go ahead an merge if you are satisfied.