Add 'Base' theme to demos

Author: mar10

lib/Super-Theme-Switcher/images/theme_90_base.png

@@ -50,6 +50,11 @@
 					name: "black-tie",
 					icon: "theme_90_black_tie.png"
 				},
+				{
+					title: "Base",
+					name: "base",
+					icon: "theme_90_base.png"
+				},
 				{
 					title: "Blitzer",
 					name: "blitzer",