elemen-ui表格组件表头复选框添加全选二字

.el-table /deep/ .DisabledSelection.cell .el-checkbox__inner{
    margin-left: -30px;
    position:relative;
  }
  .el-table /deep/ .DisabledSelection.cell:before{
    content:"全选";
    position:absolute;
    right:11px;
  }