Introduce Mypy in pre-commit

[michalslowikowski00]

Description Add Mypy in pre-commit. https://mypy.readthedocs.io/en/stable/

Use case We would like to keep our code clean and tidy -- that's why setting up Mypy in pre-commit is a good idea.

Related Issues N/A

[turbaszek]

+1 for this and I think @Humbedooh also likes the type hints!

[michalslowikowski00]

What do you think about flake8 also?

[turbaszek]

I think that if we introduce pylint #55 then we don't need flake8. We are also using black and flake8 is not always ok with black formatting - and it doesn't format the code automatically 😉