cryptol-remote-api: render docs as artifact or use simpler rst

[pnwamk]

#1207 much improves our documentation for the low-level details of the server, but the .rst generated contains some features (e.g., custom anchors) that do not render nicely in Github's file browser/explorer UI. Should we generate HTML/PDF/etc documentation artifacts as a part of the build that fully render the .rst correctly? Or consider simplifying what kind of .rst we generate?

[atomb]

We could consider rendering it to HTML (using Sphinx, maybe?) and make it available using GitHub pages.

[pnwamk]

If we render the reference manual somewhere convenient (#1260) then we could also render these docs there.