moveToTop(child) {
		const childIndex = this.getChildIndex(child);
		if (childIndex > 0) {
			const children = this.getChildren();
			// note : we use an inverted loop
			children.splice(0, 0, children.splice(childIndex, 1)[0]);
			// increment our child z value based on the previous child depth
			child.pos.z = children[1].pos.z + 1;
			// mark the container as dirty
			this.isDirty = true;
		}
	}
Move the specified child to the top(z depth).
@param {Renderable|Entity|Sprite|Collectable|Trigger|Draggable|DropTarget|NineSliceSprite|ImageLayer|ColorLayer|Light2d|UIBaseElement|UISpriteElement|UITextButton|Text|BitmapText} child - Child to be moved