Consider myst for doc rendering

[delucchi-cmu]

@bsipocz has had success with using myst, in combination with sphinx, for readthedocs rendering.

This would enable notebooks to be source-controlled as markdown files, instead of hard-to-read ipynb.

[delucchi-cmu]

From Brigitta:

here are the notebook infra: https://myst-nb.readthedocs.io/en/latest/index.html, and https://executablebooks.org/en/latest/
(and for CI: numpy-tutorials, NASA NAVO workshop, IRSA tutorials all use the same setup of nbval for pytest and myst for rendering/executing)

[bsipocz]

fwiw it all started with the astroML book as notebooks :)

(and getting up some infrastructure template is on our radar for a while with the other numpy folks, we just couldn't find the resources/time to make it happen yet)