docs: replace ryd with something less custom

[ssbarnea]

Docs should be using standard RST or MD (recently added to Sphinx) instead of "ryd". This should help a little bit with the "NIH" approach.

[smurfix]

I'd just run ryd2rst on them. These days it's certainly possible to extract the Python code from Sphinx, just mark the code blocks as Python, no need to run a nonstandard tool.

[ssbarnea]

Can you please make a PR to address the doc building?

[jwilson8767]

I'm working on this over on dev-docs. I got the initial conversion to RST done...but there is a long way to go to make these docs really useful.

[jwilson8767]

@ssbarnea Can you add me to the RTD?

[ssbarnea]

@jwilson8767 done