Add transparent neutral button

[joannaquu]

Platforms Impacted

• iOS
• macOS

Description of changes

Added a new style to Button, transparentNeutral.

Binary change

Total increase: 168 bytes
Total decrease: -8 bytes

File	Before	After	Delta
Total	30,922,584 bytes	30,922,744 bytes	⚠️ 160 bytes

Full breakdown

File	Before	After	Delta
ButtonTokenSet.o	123,376 bytes	123,544 bytes	⚠️ 168 bytes
Button.o	211,080 bytes	211,072 bytes	🎉 -8 bytes

Verification

Visual Verification

Light	Dark

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

[Saadnajmi]

@mischreiber @huwilkes Are we ok with a new variant here?

[anandrajeswaran]

Should update PR description for the updated style name?