1.仅添加复选框
<el-table-column type="selection" width="55"></el-table-column>
2.添加复选框和文字行号在一列
<el-table-column>
<template #header>
<el-checkbox v-model="selectAll" @change="handleSelectAll">全选</el-checkbox>
</template>
<template #default="{$index}">
<el-checkbox v-model="selectedRows"></el-checkbox>
<span>{{$index+1}}</span>
</template>
</el-table-column>