v2.11

Changes

• PEP 604 compliance.
• Fixed that Union[None, X] with None on the first place wasn't treated as Optional[X].
• Fixed that Union[X, T] where T was resolved to None wasn't treated as Optional[X].
• Allow using None as the field type (it's considered equivalent to NoneType).
• Changed the name of NoneType to None in Unions for convenience. In the previous versions you could see Union[int, str, NoneType] instead of Union[int, str, None] if the field was declared as Union[int, str, None].