Extend documentation: Use-cases, examples and motivation

[kljohann]

In order to better understand what benefit genpybind could provide to a project, some use cases and links to existing projects might be helpful. For example:

• Expose a C++ API to Python: This one is obvious, but can also be achieved using hand-written bindings. In addition to reducing the manual effort, genpybind helps in those cases where your interface is still undergoing regular changes, where manual bindings might be a hindrance.
• Interactive use and exploration of a library's API: Without much overhead you can add a single line in order to exercise your newly-written function using the REPL.
• Facilitated unit testing: (This is one of my favourite points.)
  • Writing tests in Python could be easier, faster or more approachable. (In addition it does not require Knowledge of C++, which might help depending on your developers'/testers' backgrounds.)
  • Unit testing libraries like https://docs.pytest.org could reduce the boilerplate involved in writing a test. It may be faster to go from interactive exploration of your implementation in the REPL to a unit test.
  • You can take advantage of property based testing using a powerful, stable and well-tested framework like https://hypothesis.readthedocs.io.
• …

Also, standalone examples and links to projects that make use of genpybind (e.g. https://github.com/electronicvisions) would likely be of interest for potential users.