Add API documentation for all functions

[Luthaf]

Now that we have a good CPU implementation for everything, we need to add API documentation for all functions!

This would need to be done in both Python & C++

• API documentation for Python
• API documentation for C++
• Setup documentation website with sphinx
• Build documentation on CI & setup preview with readthedocs

@frostedoyster could you take care of the first two items? I can do the sphinx setup!