Refactor repository into Sphinx documentation (docs) and potentially example code (src)

[baagaard-usgs]

Currently, the repository is a collection of Markdown examples. It would be nice to move the Markdown files into Sphinx style documentation to facilitate searching and navigating.

Would make it easier to embed examples, etc in text boxes, etc.

[gassmoeller]

@ljhwang and I talked about this again. Lorraine found a way to include drop-down descriptions into markdown files (see https://github.com/geodynamics/best_practices/blob/main/SoftwareDevelopmentBestPractices.md), and that may be a better way than setting up a whole Sphinx infrastructure just to be able to add examples. We can keep this open for discussion, but at least for the current update to the best practices we would leave out the sphinx infrastructure.