Review: add documentation

[cthoyt]

This code currently does not contain any documentation. There are a few ways to go about doing that to make it useful for potential users:

1. Add a "getting started" example to the README
2. Use sphinx to auto-generate documentation based on docstrings and weave them together with tutorials

See https://www.youtube.com/watch?v=azf6yzuJt54 for motivation on better documentation - there should be several parts to documentation:

1. Technical documentation (i.e., all functions are self-explanatory what they do based on their docstrings)
2. High-level documentation (i.e., tutorials for the thing 99% of users will want to do with your package after reading your paper)

[cthoyt]

This was not done

[r-costa]

Thank you for highlighting this aspect. We now provide the ReadTheDocs https://sbml2hyb.readthedocs.io/en/latest/# .