feat: Consider adding py.typed file marker for type-checking support

[FBruzzesi]

Currently mypy raises a warning when importing semhash:

Skipping analyzing "semhash": module is installed, but missing library stubs or py.typed marker [import-untyped]
from semhash import SemHash
^
[...]: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports

[Pringled]

Hey @FBruzzesi, thanks for reporting, we'll add this soon!