Add ContentIsland page with Helmet demo (requires WinAppSDK 1.7 APIs)

[JesseCol]

NOTE: Do not merge until WinAppSDK is updated to 1.7.

Description

Adds a ContentIsland page that uses Scene Node APIs to show a 3D model of a helmet.

Motivation and Context

This shows how apps can use ChildSiteLink to attach a ContentIsland in a Xaml app.

How Has This Been Tested?

• Built and ran packaged
• Built and ran unpackaged

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[ionvasilian]

You'll also need to set the childSiteLink's LocalToParentTransform to match the transform from the placementVisual to the parentIsland's rootVisual.

[jeffstall]

Can we just check into the experimental branch now, and then merge that branch into main once WASDK 1.7.0 is GA?

[niels9001]

@JesseCol I've updated your PR to resolve major conflicts due to #1732. I've also tweaked the XAML a bit to remove unnecessary XAML and used a WrapPanel vs. the Grid so things are easier to see on a wide-screens.

[JesseCol]

Can we just check into the experimental branch now, and then merge that branch into main once WASDK 1.7.0 is GA?

Hi, there's no dedicated experimental branch for this repo (WinUI-Gallery). I've heard there's a new plan for WindowsAppSDK-Samples where we'll check in code that uses experimental APIs to main, and then conditionally compile that code. Maybe we can do something similar here.

[marcelwgn]

Can we just check into the experimental branch now, and then merge that branch into main once WASDK 1.7.0 is GA?

Hi, there's no dedicated experimental branch for this repo (WinUI-Gallery). I've heard there's a new plan for WindowsAppSDK-Samples where we'll check in code that uses experimental APIs to main, and then conditionally compile that code. Maybe we can do something similar here.

For that, we essentially only need to check for WinUI 1.7 in the csproj and .cs file right?