Consider switching sphinx build github action

[cjgrady]

Is your feature request related to a problem? Please describe.
The github action we are using for building sphinx docs does not have support for pre-build commands. We need to be sure to update the api docs before running the sphinx build so that the latest code documentation is included (important if we change functions / modules / etc, not so if we update code within existing). The following command does this:

sphinx-apidoc -f -o _sphinx_config/source lmtest

I have also added this to the Makefile for make html calls.

We are currently using the Sphinx-notes pages GitHub action and it does not support pre-build commands or using our Makefile.

We have a couple of options that could do this though

1. We could use https://github.com/ammaraskar/sphinx-action, which does support pre-build commands as well as some partner actions for uploading outputs. We may need to use a combination of these two actions to continue automatically updating GitHub pages.
2. We could add a pre-commit or something to force that the api docs files are updated before committing
3. We could implement our own GitHub action to build sphinx docs and include any necessary prerequisite steps