Colors, Contrasts, and now ready for LinuxMint 21

• MintSoda new color 3DB884 (HSL = 155,50,48 | contrast = 2.5)
• GTK-3 outlines on focused buttons only
• GTK-4 window controls (min/max/close) update
• Other small GTK-4 updates based on GTK-3 Meld comparisons