设置全局滚动条样式

  ::-webkit-scrollbar{
    width: 4px;
    height: 6px;
  }
  ::-webkit-scrollbar-corner{
    display: block;
  }
  ::-webkit-scrollbar-thumb {
    border-radius: 8px;
    background-color: rgba(0,0,0,0.2);
  }
  ::-webkit-scrollbar-track{
    border-right-color: transparent;
    border-left-color: transparent;
    background-color: rgba(0,0,0,0.1);
  }