ReactiveX for Python (RxPY) v4

[dbrattli]

Please try the new ReactiveX for Python pre-release:

pip install reactivex --pre

Changes:

• Package is renamed from rx to reactivex. To use as before import reactivex as rx.
• Generic type annotations for Pyright/Pylance and Mypy. Pylance works at strict settings.
• Pipe function is renamed to compose. The pipe method is still the same, and there´s also a new pipe function that pipes similar to the method.