Dev docs

[fmizzell]

As I am going through our tests and the whole codebase, I still, often, feel like we do not have a north star nor well defined boundaries to help us organize our codebase. I think that some documentation that more specifically looks at what a module is supposed to do and how it is organize could serve as the boundary setter, and also as a point of conversation to what belongs or does not.

This PR creates a possible way for us to start organizing this type of documentation.