[SA Mod Manager] [suggestion] add a resolution scale feature for SA Mod Manager

[CODEX0827]

from time to time i find that the SA Mod Manager font is just to small to read clearly so add an option to change the resolution scale it can really boost accessibility for the program

[PiKeyAr]

For me the font size is too big. I agree a global UI scale option would be nice. However, according to #239, it's not planned at the moment.

[ItsEasyActually]

The font is size 13, it was a compromise for wanting a more legible font, but it means the UI has to have the font at 13 or the UI "breaks." We changed the font early on, but the theming for the app ended up not being ideal for changing the font size afterwards. That's mostly because we were learning WPF as we built this and plenty of mistakes were made along the way.

The good news is that the in progress Avalonia theme we will eventually be using has better font size handling support. I'm hoping to take advantage of that for better accessibility settings when we move over.