按钮背景图片闪动5秒然后停住

按钮背景图片闪动5秒，然后停住：

@keyframes flashing {
      0%, 100% {
          filter: grayscale(0%);
      }
      50% {
          filter: grayscale(50%);
      }
    }
    .alarmBg {
        color: #E93557;
        background: url('../../../assets/images/newui/alarmBg.png') no-repeat;
        border: none;
        // animation: flashing 5s infinite;
        animation: flashing 0.4s linear 13;
    }