0.16.1: Fix GTK+3.20 button and add Gnome-Colors/Shiki colorschemes

982d678 chore(colors): add all gnome-colors a.k.a. shiki
0eaf17d fix(gtk3.20: button): disabled button (especially in dark colorscheme)
32c2f22 fix(gtk3.20: button): border for light colorscheme