Add Type Hinting

Currently importing RESQPY into a python file in another project and running the [Mypy](https://mypy.readthedocs.io/en/stable/index.html) type checker generates a series of errors: `error: Skipping analyzing "resqpy": module is installed, but missing library stubs or py.typed marker [import]`. This is because Mypy cannot detect the types present in RESQPY due to a lack of type hints.

The issue names no source files, tests, or entry points; begin by locating the resqpy package and determining the intended Mypy support scope. Done means Mypy no longer reports the missing stubs or py.typed marker error when RESQPY is imported from another project.

Written by the indexing model from the issue text.