[review] API documentation

I appreciate the use of type hints and mypy to document the API internally in the code (this is always very nice to me). I also see that the examples/api example files do appear to demonstrate the API for the most part. However, I feel this does not really cover the API documentation.

I would like to see reference API documentation which describes the functions, objects, and methods including a description of variables, inputs, and/or outputs akin to what we see for numpy, scipy, or astropy. If one uses RTD and/or sphinx to generate documentation as I suggested in #34 (closed), the docstrings for the python objects themselves can be automatically turned into these types of documentation pages using tools like sphinx-automodapi.