Big docs update

[cboulay]

• Most of the prior API and Utils docs has been moved into the src docstrings and the docs are now populated with autodocs.
• Added many new docstrings to modules in sigproc
• Generated new docs from sigproc docstrings.
• [source] links back to GitHub.
• I tried to link objects to eachother but this was hit-or-miss.

This is a very large PR but there are absolutely no code changes (unless you count Sphinx conf.py).

IMO, the best way to review it would be to check out the branch, build the docs, and explore a bit.

[griffinmilsap]

WHOA! Awesome!

I'll start poking through this; @peranpl1 has been looking into using ChatGPT to generate documentation for what its worth. I'll also want to contribute some high level "getting started" type introduction documentation

[cboulay]

Attaching the built docs here for others to download:

ezmsg_docs.zip

Download, upack, and open index.html.

[griffinmilsap]

BIG THANKS for this contribution. I read through a bunch of this and it is all VERY helpful!