Add a GitHub Actions job to format Python code

[laysauchoa]

This seems like a good idea. I'd recommend black formatter for python code as it is the standard and the default for python code.

Reference: https://pypi.org/project/black/

[lornajane]

(triaging the issue list which made me read this one again). We've also talked recently about having testable code, I suggest we move all code to the code/ folder so we can work on it outside the RST context, and then include the code in the articles as needed. Just mentioning this as a pointer for when we do prioritise this work.

[laysauchoa]

Great point, I will change the proposal here to cover only .py files which can be done independent from .rst embedded code. This should reflect in how the code is displayed as long as we are using from the code to the .rst format.