[Editor] Add lacking input() method to generated map handler

editor/src/main/resources/java_templates/map_handler.ftl

@@ -17,6 +17,11 @@ public class ${className} implements MapHandler {
 
    }
 
+   @Override
+   public void input(Window window) {
+
+   }
+
    @Override
    public void update(Context context, GameMap map, float dt) {