formal API documentation

[jGaboardi]

• detailed & complete docstrings for all top-level namespace funcs?
  • tracked in testing, refactor, & docstrings #20
  • need more explanation for *_threshold_* params in simply.simplify_network() #110
  • others?
• docs/{conf.py, *.rst}
• Read the Docs?

[jGaboardi]

• check out foliums doc style
• @martinfleis says to maybe base on books theme?

[martinfleis]

This is the theme - https://github.com/executablebooks/sphinx-book-theme. I am using it for Xvec among other. No clue how to do the version switcher with that one, folium is using pydata theme which has it included. Let's start with the basics without it and we can re-iterate later. The GHA could be possibly based on those we have in PySAL? Or check the one in folium. That one is neat.