Add py.typed marker to incidate repro-zipfile is typed

[miikka]

Hi! I'm using a repro-zipfile in a small project and running mypy gives the following warning:

error: Skipping analyzing "repro_zipfile": module is installed, but missing library stubs or py.typed marker  [import-untyped]

I noticed that repro-zipfile actually does have type definitions, but it's missing the py.typed marker file. Could you consider adding it?

There's the small hurdle that PEP-0561 does not really have a way for marking a single-file packages as typed. It says:

This PEP does not support distributing typing information as part of module-only distributions or single-file modules within namespace packages.

The single-file module should be refactored into a package and indicate that the package supports typing as described above.