[Feature request] Allow pipe ( "|" ) to be used as a shortcut for Union

[ksamuel]

Union are a very common situation when typing code, but they require an import every time. I usually can get away with str/int/float or my own classes for most of the code, but end up making an import just for Union, Dict and List.

The idea would be to allow Union to be expressed with a "|", replacing the Union:

from typing import Union

def multiply(*values: Union[int, float]) ->  Union[int, float]:

Would become:

def multiply(*values: int|float) ->  float|int:

[emmatyping]

This would normally be a discussion for the typing tracker, but it has been rejected several times. Closing as not about mypy.