fix: add py.typed for type checkers

[ydcjeff]

See colab.

Description:

Check list:

• New tests are added (if a new feature is added)
• New doc strings: description and/or example code are in RST format
• Documentation is updated (if required)

[vfdev-5]

For context:

• https://mypy.readthedocs.io/en/stable/installed_packages.html#creating-pep-561-compatible-packages
• https://blog.whtsky.me/tech/2021/dont-forget-py.typed-for-your-typed-python-package/

If you use setuptools, you must pass the option zip_safe=False to setup(), or mypy will not be able to find the installed package.

@ydcjeff any thoughts about this note from mypy docs

Can you also add a test step similar to the one you have in the colab ?

[ydcjeff]

Can you also add a test step similar to the one you have in the colab ?

I think this is not needed once we confirm it is working.

[vfdev-5]

Can you also add a test step similar to the one you have in the colab ?

I think this is not needed once we confirm it is working.

There will be also failure for other domain libs like torchvision. OK for keeping this PR without test step.

Saw that MONAI does the same: Project-MONAI/MONAI#626

[vfdev-5]

Thanks @ydcjeff !