Ensure strong type hinting

By the nature of the computation done in this library, it is compelling to take shortcuts while prototyping. While this is a good thing and speeds up development, it should be required that production code be type hinted in a strict fashion; by doing so not only IDEs and code editors can help with the code, bugs can be caught through linting and type checking, which means better production code overall, faster, and more secure.

• Add linting / type checking in CI #20 (closed)
• Write developer documentation on the standards to follow #22