Support for proportional fonts

[merchako]

I ran Ligaturizer on the included Plex Sans (proportional). Unfortunately, the ligatures are making bad overlaps with neighboring characters.

My best guess is that the editors (VS Code and TextEdit) allot the space they would give for the pre-ligatured characters, and this looks especially bad because two or three of Plex Mono characters take up way more space than the same number of Plex Sans proportional characters. I'm assuming this is a problem with the font (not the editor) since I'm experiencing the same problem in both VSCode and TextEdit.