Include py.typed in package

[streadway]

This helps type checkers identify that imports from ipware are typed so that untyped imports do not need to be ignored for statements like:

from ipware import get_client_ip

utils/http.py:8: error: Skipping analyzing "ipware": module is installed, but missing library stubs or py.typed marker  [import-untyped]
utils/http.py:8: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports