Reduce contrast of shortcut tree cells to better match non-opaque trees

Fix contrast in settings popups

Increase minimal possible margin for flat buttons

Fix light theme contrast check

Update README.md

Add missing hover-pressed states to some buttons

Update README.md

Merge branch 'main' of https://github.com/passivestar/godot-minimal-t…

…heme

Reduce selected property background opacity

Make separators in popup menus more readable