Add Type Hints to Response and Arguments of a function

[JVGC]

I just started using the package, and one thing I notice is that it's missing type hints for what the function should expect as arguments and what it actually returns.

I would say that adding that would be a really useful thing, specially because would allow me to only look for the notion api documents in special cases.

[ramnes]

Closing in favor of #199. Some work has been done in #200 and this branch, feel free to work on top of these if you want to contribute and maintain these types. Thanks!