边框渐变

 &::after {
      content: "";
      position: absolute;
      bottom: -8px;
      left: 0;
      width: 100%;
      height: 1px;
      background: linear-gradient(
        90deg,
        rgba(64, 158, 255, 0.8),
        rgba(109, 173, 239, 0.6),
        rgba(0, 255, 255, 0)
      );
    }