Fix type hints

[MaxGyver83]

I'm playing around with Cython to see if this can improve the performance. Cython is strict about types and gave me some errors, for example:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "main.pyx", line 123, in main.main
    varLetters = getVariableLetters(letters_L1, staticLetters)
TypeError: Argument 'staticLetters' has incorrect type (expected str, got tuple)

This pull request fixes all TypeErrors Cython complained about.

[Glitchy-Tozier]

1. Thank you for the PR :)
2. Just to make sure you know about the feature: Are you aware that pypy speeds up the script by a lot? If no, see README.md
3. Most of the changes make perfect sense. I'll individually comment on the two areas that I don't understand.

[MaxGyver83]

1. Thank you for the PR :)
2. Just to make sure you know about the feature: Are you aware that pypy speeds up the script by a lot? If no, see README.md
3. Most of the changes make perfect sense. I'll individually comment on the two areas that I don't understand.

1. My pleasure.
2. Yes, I'm aware of this and I only use pypy3. But it still needs a lot of time. On my laptop, 13 minutes with the default configuration. When I play around with the configuration, I need many runs. Then it sums up. That's why faster would be better :-D
3. OK, I'll answer your comments.

[Glitchy-Tozier]

Merged 👍🏻