Guide for new team members to get started with development and test contributions

Include nerdwallet guide points as appropriate, pep8, show how we deviate and why. This can be a large writeup to teach teammates how to contribute code to the repos that are our responsibility.

https://www.nerdwallet.com/blog/engineering/5-pytest-best-practices/

Also consider a style guide that can be ingested into a linter and/or formatter. Some of this might be more appropriate for an epic.