Scaling doesn't work correctly for High-DPI displays

[donnielrt]

Hi,

Thanks for this amazing theme, makes logging in much more fun and interesting :heart:

It seems like the fixed font size in the conf makes scaling not work correctly on high-DPI displays. I have a 4K OLED screen, and the purple_leaves background looks perfect, while the cyberpunk.conf or black_holes.conf theme looks tiny. If I remove the fixed FontSize="12" and replace it with FontSize="" in any of the themes with scaling issues, they seem to load fine on my display.