Add a button-style for subtle highlighting
and use it to subtly highlight commonly used symbols in the accent-views of the German layouts.
Screenshots - before this change
Adwaita:dark (Phosh's default for Squeekboard)
High contrast
Default
Screenshots - after this change
Adwaita:dark (Phosh's default for Squeekboard)
High contrast
Default
Based on !635 (merged) .
Edited by MoonlightWave-12