There's a few ways to do this but I think it would be best if the documentation is embedded in the code somehow. Do we want per feature documentation or just an overview of how a feature works? If it's per feature we could either add to the modules that create the features or inline it with each feature in the list of feature ids here: #926.

Just a quick, general overview of how modules & features work in the separate doc is enough, the details (where needed) would be inside docstrings.

Basically just discussing how the interfaces are designed and expected to be used.

Done in #968