Reviewing

Install documentation dependencies: pip install ".[doc]"
Generate the documentation: sphinx-build -M html docs/source docs/build
Open the generated HTML docs: ./docs/build/html/index.html. Hopefully it looks like this:

rashdf-docs

Notes

I tried to set this up so that things are pretty easy to slip into the documentation.
If you add a new method in RasPlanHdf for example, just make sure it has a docstring and then add the method name to ./docs/source/RasPlanHdf.rst and it should automatically get picked up by Sphinx.
Personally I'm not super concerned about the actual content of the docs at this point. More concerned about just getting documentation builds working.
This is new territory for me... chances are high that I've overlooked something.