Add Type Hinting support/ Implement PEP 561 #54

It would be useful for users who wish to use tools such as MyPy to have typing support. Ideally, the calls would be fully type-hinted, and with the inclusion of py.typed, the package would be fully compatible with PEP 561.

If instead, you prefer to do it using stubs, as noted in https://peps.python.org/pep-0561/#stub-only-packages , I have generated some stubs that i use in projects i help maintain. They are available at https://github.com/ABaumher/VDF_Typing . If you have a proper destination for the stubs i can probably draft up a Pull Request to add them in.