restructured extra directory

extra/templates/gtk/gtk.css

@@ -0,0 +1,18 @@
+@define-color accent_color {accent};
+@define-color accent_bg_color {accent};
+@define-color accent_fg_color {on_surface};
+@define-color window_bg_color {background};
+@define-color window_fg_color {foreground};
+@define-color headerbar_bg_color {surface};
+@define-color headerbar_fg_color {on_surface};
+@define-color popover_bg_color {surface_variant};
+@define-color popover_fg_color {on_surface_variant};
+@define-color view_bg_color {background};
+@define-color view_fg_color {foreground};
+@define-color card_bg_color {surface};
+@define-color card_fg_color {on_surface};
+
+@define-color sidebar_bg_color {surface_variant};
+@define-color sidebar_fg_color {on_surface};
+@define-color sidebar_border_color @window_bg_color;
+@define-color sidebar_backdrop_color @window_bg_color;

extra/templates/gtk/readme.md

@@ -0,0 +1,15 @@
+# GTK
+
+1. Download the [template file](gtk.css)
+
+2. Configure the template in `~/.config/clrsync/config.toml`:
+
+```toml
+[templates.gtk]
+enabled = true
+input_path = '~/.config/clrsync/templates/gtk.css'
+output_path = '~/.config/gtk-3.0/gtk.css'
+reload_cmd = ''
+```
+
+3. Restart GTK applications to apply the theme