[Feature Request] New Navigation Bar to Mimic win ui Behavour In Shell

### Description

Win Ui navigation as per the win ui gallery app sample shows a left-hand navigation menu that allows child items, it shows that there are child items underneath by allowing a graphic to represent open and close.


As you can see the navigation menu item has a root node and the ability for child nodes. The child nodes should allow the ability to have an icon and text and then the link itself which would be another page.

Also the controls should allow animations of opening and closing a section as per WIn UI Gallery sample app found at this repo

https://github.com/microsoft/WinUI-Gallery

It could well be this should be a control separate to shell

### Public API Changes

I suggest that we should have a tag under the shell content called subitem or child item

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### Intended Use-Case

I believe that if Win ui is to be fully supported route then we need to have child items to behave in the same manor as win ui desktop currently does. I only believe this should be one level deep and for us not to get into the same mess of web menus and allow unlimited levels of menus.