feat(draggable): allow ignore_dragging config option to be a function

src/jquery.draggable.js

@@ -14,7 +14,7 @@
         limit: true,
         offset_left: 0,
         autoscroll: true,
-        ignore_dragging: ['INPUT', 'TEXTAREA', 'SELECT', 'BUTTON'],
+        ignore_dragging: ['INPUT', 'TEXTAREA', 'SELECT', 'BUTTON'], // or function
         handle: null,
         container_width: 0,  // 0 == auto
         move_element: true,
@@ -387,6 +387,10 @@
             return !$(event.target).is(this.options.handle);
         }
 
+        if ($.isFunction(this.options.ignore_dragging)) {
+            return this.options.ignore_dragging(event);
+        }
+
         return $(event.target).is(this.options.ignore_dragging.join(', '));
     };