Update README.md

Added missing comma

Author: LukyVj

README.md

@@ -116,7 +116,7 @@ let magicGrid = new MagicGrid({
   gutter: 30, // Optional. Space between items. Default: 25(px).
   maxColumns: 5, // Optional. Maximum number of columns. Default: Infinite.
   useMin: true, // Optional. Prioritize shorter columns when positioning items. Default: false.
-  useTransform: true // Optional. Position items using CSS transform. Default: True.
+  useTransform: true, // Optional. Position items using CSS transform. Default: True.
   animate: true, // Optional. Animate item positioning. Default: false.
 });
 ```