Turn neuralsa into installable package

[tomaz-suller]

Using Hatch I restructured the repository to allow anyone to install it. This avoid having to deal with the $PYTHONPATH to add the code as a dependency, as the README now instructs, which is quite cumbersome.

I've left this as a draft since there's a few things I think make sense ironing out before merging

• Add the right contact information for the authors
• Update the README
• Define what the public API should be
• Add docstrings to public-facing API
• Add more type hints