Ship a py.typed file to indicate inline type information

[Qrashi]

This library seems to have full inline typing information, mypy runs without errors even with

warn_return_any = true
warn_unused_configs = true

removed from pyproject.toml.

But when i use the library and run mypy i get [import-untyped] errors even tough the library has inline typing information.

Ship a py.typed file according to pep 561 to indicate that the package supports typing.