Add Sphinx document generation and publish to readthedocs.io

* https://www.sphinx-doc.org/en/master/
* You probably want to use exhale which allows you to do Doxygen - https://exhale.readthedocs.io/en/latest/
* You might also find the following extensions useful;
- https://github.com/mithro/sphinxcontrib-session
- https://github.com/SymbiFlow/sphinxcontrib-verilog-diagrams
- https://github.com/SymbiFlow/sphinx_materialdesign_theme

Example of how to set this up can be found at https://github.com/SymbiFlow/sphinxcontrib-verilog-diagrams/tree/master/docs and https://github.com/SymbiFlow/sphinxcontrib-verilog-diagrams/blob/master/.readthedocs.yml

Review the linked Sphinx and exhale documentation, then compare the referenced docs directory and .readthedocs.yml examples. Define the repository's Sphinx generation and Read the Docs setup, including any useful extensions, and verify that the generated documentation publishes successfully.

Written by the indexing model from the issue text.