flex布局，左侧随着右侧高度变化而变化

下面是经典的elementui布局容器

<el-container>
    <el-header>Header</el-header>
    <el-container>
      <el-aside>
        <leftSide></leftSide>
      </el-aside>
      <el-main>
        <router-view/>
      </el-main>
    </el-container>
  </el-container>

css核心是给.el-container加align-items: stretch;
布局css如下

.el-header {
  background-color: #B3C0D1;
  color: #333;
  height: 60px;
}

.el-container {
  align-items: stretch;
  min-height: calc(100vh - 60px);

  .el-aside {
    background-color: #D3DCE6;
    color: #333;
  }

  .el-main {
    background-color: #E9EEF3;
    color: #333;
  }
}