Reduce window minimum size

[Poent]

Hello,

Currently Mu Editor sets it's minimum window size as half the screen width and height. This is unnecessarily restricts user customization and is especially noticeable on high resolution monitors and ultra-wide screens.

This restriction is currently implemented under interface/mu/main.py, line 1139
self.setMinimumSize(screen_width // 2, screen_height // 2)

I recommend that line 1139 be adjusted to:
self.setMinimumSize(screen_width // 4, screen_height // 4)