Method add

packages/fairygui/src/core/Timer.ts:76–78

* Add a callback to be called each frame * 添加每帧调用的回调

(callback: Function, caller: any)

     * 添加每帧调用的回调
     */
    public static add(callback: Function, caller: any): void {
        Timer.inst.frameLoop(1, caller, callback);
    }

    /**
     * Remove a callback