Add static type checking

[n1rna]

I have recently started using bitcoinlib in my projects and really appreciate the work that's been done so far. But it was hard not to mention that the library is missing type checking features. This can be a huge advantage if added to the library and I would say it needs to be added sooner rather than later. The more features implemented without the type checking features, it will be harder to refactor in the future.

Wanted to hear your thoughts on this topic and see if there are any plans yet. Since I've started using bitcoinlib in one of my projects extensively, I would like to contribute to the progress of the work on that topic if necessary.