docs(envvars): Automatically update environment files

[samoehlert]

Closes #81

This includes:

• a script to parse environment variables (a bit of a nasty regex, I'm not sure how else to do it)
• associated tests
• the docs themselves
• convenience Makefile target
• precommit hook that runs the Makefile target so each commit theoretically has the latest variable CRUDs
• finally precommit was upset at me for not having the python-version

Also ruff formatting changed a couple of whitespace things, whatever.