Add a11y labels

[DandyLyons]

This PR adds accessibility labels to make the camera usable for Voice Control and VoiceOver users etc.

This PR should close #100

[DandyLyons]

Room for Improvement

When I have bandwidth I hope to make the following improvements in another commit to this PR.

• The toggle buttons should have an a11y toggle trait
• The circular buttons should have a circular a11y focus indicator
• Add a11y support for zoom in/out
• the app should announce key events like when an image is taken, when camera orientation has changed, when a filter has been applied/unapplied
  • (It would also be nice if the app announced what the camera is pointed at before taking a picture. This is ambitious but possible and would most likely require realtime streaming data from Mijick Camera, so this probably not a trivial feature to implement).

The implementation for most of these features should be fairly trivial and the implementation details can be found in this WWDC video:
Build accessible apps with SwiftUI and UIKit - WWDC23 - Videos - Apple Developer