visionOS support

[guygodin]

Description

Now that the Vision Pro is available publicly to customers, I think adding the ability to target visionOS in .NET MAUI would be very valuable. MAUI already supports targeting iOS, tvOS and watchOS devices.

Public API Changes

///

/// Gets an instance of that represents Apple visionOS.
///

public static DevicePlatform visionOS { get; } = new DevicePlatform(nameof(visionOS));

Intended Use-Case

Having the ability to deploy existing iOS apps to the Vision Pro as Window apps could be a first, easier feature to add. Later updates could add support for volume and eventually immersive space apps as those need to expose a broader range of APIs.