Docs fixes

[Sebanisu]

resolves: https://github.com/codereport/jsource/issues/216

I'm taking some things I learned from adding docs on my repo and applying it to yours.

• Unrelated I also added code to cmake to make it go git the submodule for me.
• Add myst_parser, remove the preprocessor.py
  • I couldn't get this to work. myst_parser supports .md files.
• GLOB_RECURSE more things. these are DEPENDS so that cmake knows to rerun sphinx or doxygen if these files change.
  • was just .h files
  • now checks .cpp, .c, .hpp
  • Also .rst and .md
• doygen disable HTML and LATEX as sphinx only uses XML
• set source_suffix so sphinx knows to check both .md and .rst files.
• made a verbs.md and left verbs-old.rst so you could compare.
• updated FindSphinx.cmake to make it more likely to find sphinx. pip installs it to your home folder on ubuntu. So I gave it some hints of places to look.