[Proposal]: `FlowLayout` Sample `winAppSDK 2.0`

### Issue type

sample request

### Which version of the app?

WinUI 3 Gallery

### Description

https://learn.microsoft.com/en-us/windows/windows-app-sdk/api/winrt/microsoft.ui.xaml.controls.flowlayout?view=windows-app-sdk-2.0-experimental

### Screenshots

_No response_

### Windows version

_No response_

### Additional context

_No response_