Add typehints

[alkatar21]

It seems that the project is dead?

If not, at least basic typhints would be desirable as it becomes more common to use typechecker and it generally makes libraries more usable.

[lkiesow]

I agree, but while I will occasionally look after this and create new releases, I don't have a lot of time to spend on this. That being said, I'm not saying no to a pull request introducing type hints if someone wants to provide that.