Container components for scaffolding basic structure of the page:
`<el-container>`: wrapper container. When nested with a `<el-header>` or `<el-footer>`, all its child elements will be vertically arranged. Otherwise horizontally.
`<el-header>`: container for headers.
`<el-aside>`: container for side sections (usually a side nav).
`<el-main>`: container for main sections.
`<el-footer>`: container for footers.
:::tip
These components use flex for layout, so please make sure your browser supports it. Besides, `<el-container>`'s direct child elements have to be one or more of the latter four components. And father element of the latter four components must be a `<el-container>`.
| direction | layout direction for child elements | string | horizontal / vertical | vertical when nested with `el-header` or `el-footer`; horizontal otherwise |