GNOME 3.2x Arc theme tweak

Content: 1.5x dpi, prefer white transparent bg

arc-gnome-shell-append.css

arc-gtk-3.0-append.css

1.5x assets: https://www.dropbox.com/sh/u9pb7zra8odp3c0/AACrUz7rA2LkyKdV4Mfc7gZva?dl=0