Add typing integration

[enzo-santos]

This PR adds integration with the typing module, specifically the specifications proposed by PEP 612.

This PR also makes some decorators to return the value returned by the wrapped function (such as trycatch and timer), so you can use them such as

import decorators

@decorators.timer
def calculate(foo: int) -> int:
    return foo + 42

print(calculate(21))    # Previous version: prints None
                        # Current version: prints 63

The code is checked by mypy and is also formatted by black.