[Fluent 2 iOS] Add ShadowTokensDemoController to demo app

[laminesm]

Platforms Impacted

• iOS
• macOS

Description of changes

ShadowTokensDemoController was added to the demo app to display shadow tokens. Each shadow is displayed on a CardView. The users can toggle between elevation shadow (Shadow 1) and border shadow (Shadow 2).

Verification

Before	After

Shadow 1	Shadow 2

Pull request checklist

This PR has considered:

• Light and Dark appearances
• iOS supported versions (all major versions greater than or equal current target deployment version)
• VoiceOver and Keyboard Accessibility
• Internationalization and Right to Left layouts
• Different resolutions (1x, 2x, 3x)
• Size classes and window sizes (iPhone vs iPad, notched devices, multitasking, different window sizes, etc)
• iPad Pointer interaction
• SwiftUI consumption (validation or new demo scenarios needed)
• Objective-C exposure (provide it only if needed)

Microsoft Reviewers: Open in CodeFlow

[sophialee0416]

Could we get dark mode screenshots?

[laminesm]

Could we get dark mode screenshots?

The description is updated with dark mode screenshots.

[Saadnajmi]

(Chiming in from the FURN side) Is there a way in the demo controller to see both shadows combined on one view? Not obvious to me there is one from the screenshots.

[laminesm]

(Chiming in from the FURN side) Is there a way in the demo controller to see both shadows combined on one view? Not obvious to me there is one from the screenshots.

In this demo they are not combined. You can just toggle between the border shadows and the elevation shadows.