Speed up sphinx builds

[wd60622]

It would be awfully convenient to be able to build a single notebook, only the notebooks, or specific module docstrings.

The make html command is very helpful. However, the build takes some time

https://github.com/pymc-labs/pymc-marketing/blob/91564cfbcce3d341d3d9bdab91a5b25766764b5a/Makefile#L20-L22

For notebooks, the sphinx rendering is a bit different than the jupyter notebook which can cause render issues not seen.

Not sure if this is possible though!