Add type hint for python module.

[baseplate-admin]

Hi there, Sorry for pinging you in Christmas. ( Merry Christmas ). I hope you are having a good day.

I am using your awesome library minify-html for my module

While working on this i had to refer to the underlying rust module several times to get all the options.

Now I think it would be better to add type hint to the module to make it a bit developer friendly. As discussed here it should be very easy to add type hint to PyO3. I already forked this project and added the .pyi file according to this dummy repo from maturin.