update doc

src/Facade/Payment.php

  * @method static bool verifyGatewayReturn(Request $request)
  * @method static bool verifyGatewayCallback(Request $request, Response &$response = null)
  * @method static string|null getBillIdFromRequest(Request $request)
+ * @method static int|null getBillStatus(Request $request)
+ * @method static bool|null isBillSuccess(Request $request)
+ * @method static bool|null isBillFailed(Request $request)
+ * @method static bool|null isBillPending(Request $request)
  */
 class Payment extends Facade
 {