moveToBottom(child) {
		const childIndex = this.getChildIndex(child);
		const children = this.getChildren();
		if (childIndex >= 0 && childIndex < children.length - 1) {
			// note : we use an inverted loop
			children.splice(
				children.length - 1,
				0,
				children.splice(childIndex, 1)[0],
			);
			// increment our child z value based on the next child depth
			child.pos.z = children[children.length - 2].pos.z - 1;
			// mark the container as dirty
			this.isDirty = true;
		}
	}
Move the specified child the bottom (z depth).
@param {Renderable|Entity|Sprite|Collectable|Trigger|Draggable|DropTarget|NineSliceSprite|ImageLayer|ColorLayer|Light2d|UIBaseElement|UISpriteElement|UITextButton|Text|BitmapText} child - Child to be moved