Modify setter to ensure that the type of config.window_size is a tuple[int, int].

[henrikmidtiby]

Overview: What does this pull request change?

The intention with the PR is to simplify the code of Manim.

The idea came from this comment #4230 (comment) by @chopan050.

The main issue is that a cyclic import hinders the code in running.
Any ideas of how to solve this will gladly be received.

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested