Spell check

[rwegener2]

There are a lot of spelling errors in the repo (See #15, #16, #17, ... 😅), and it would be great to enable a spell checker to help catch these and other spelling errors.

Sphinx has a spelling extension that might work for this project:

https://sphinxcontrib-spelling.readthedocs.io/en/latest/

The installation instructions for the extension are here. This project is using Juptyer Book which is built on top of sphinx, so we will be modifying the setup slightly following the Advanced Sphinx usage section of the jupyter book docs. Once its installed we can try to run the spell check as described here.