Added docs

Author: photonstorm

src/input/CreateInteractiveObject.js

@@ -22,7 +22,7 @@
  * @property {boolean} enabled - Is this Interactive Object currently enabled for input events?
  * @property {boolean} draggable - Is this Interactive Object draggable? Enable with `InputPlugin.setDraggable`.
  * @property {boolean} dropZone - Is this Interactive Object a drag-targets drop zone? Set when the object is created.
- * @property {?Phaser.GameObjects.GameObject} target - [description]
+ * @property {?Phaser.GameObjects.GameObject} target - An optional drop target for a draggable Interactive Object.
  * @property {Phaser.Cameras.Scene2D.Camera} camera - The most recent Camera to be tested against this Interactive Object.
  * @property {any} hitArea - The hit area for this Interactive Object. Typically a geometry shape, like a Rectangle or Circle.
  * @property {HitAreaCallback} hitAreaCallback - The 'contains' check callback that the hit area shape will use for all hit tests.