Improve the Python type annotations for fitz_new

[indigoviolet]

Is your feature request related to a problem? Please describe.

Python type hints (which can be validated using mypy or Pylance in vscode) are very helpful; fitz_new has much better coverage than fitz in this regard. However several methods are dynamically assigned (eg. Page.get_text is assigned from utils.get_text). These types are not visible to the typechecker.

Describe the solution you'd like
Use a type stub file to describe the type signatures of these functions so that typecheckers can see them, and include the typestub in PEP 484/561 - compliant fashion.

Thank you!

[indigoviolet]

Alternatively, instead of the dynamic assignment, use some kind of mixin class, or make the utils functions the dynamically assigned ones (since the docs all refer to the Page/Document class methods)