Multipage App Menu(Navigation) Position from vertical to Horizontal

#### Implementation scenario:
I want to change APP menu from vertical to horizontal

#### Existing problems:
I tried Multi-page App type, it's working fine, is it possible to change the Menu(Navigation) position to Horizontal

#### Current plan:
Please paste the complete amis schema code of your current scheme...

```
{
"type": "app",
"brandName": "应用名称",
"pages": [
{
"label": "分组1",

"children": [
{
"label": "父页面",
"url": "/parent",
"children": [
{
"label": "子页面",
"url": "pageA",
"schema": {
"type": "page",
"title": "Page A"
}
}
]
}
]
}
],
...
}
```

Reproduce the supplied multi-page app schema and inspect how the app menu is rendered and positioned. Determine the supported navigation layout options and verify the result with a multi-page app using the provided nested pages; done means the menu is displayed horizontally without breaking navigation.

Written by the indexing model from the issue text.