[Feature]: Mica as control background for WinUI3

[Diegorro98]

Describe the feature/enhancement you need

Create an option that allows the developer to enable a mica background for the WebView2 control at WinUI3.

I've saw that there are ways to do it at #3439, but they are kind of complex. But now that in the Flexible System Backdrop Placement feature is live on Windows App SDK experimental 2 release, maybe it can be achieved easily

The scenario/use case where you would use this feature

Enabling transparence on the visited webpages would show the mica backdrop, achieving more integration with Windows and feeling more native.

How important is this request to you?

Nice to have. There are other ways to tackle this, but having official API support would be beneficial.

Suggested implementation

https://learn.microsoft.com/en-us/windows/apps/windows-app-sdk/experimental-channel#flexible-system-backdrop-placement

What does your app do? Is there a pending deadline for this request?

No response