Implement ⌚️ notification UI

[kirb]

Still not 100% sure on how this will work. Looks like everything is correct in the build process; we just need to somehow invoke adding the app to the watch.

[kirb]

Should be possible now that I worked out how to load app extensions for Canzone. Theos can build directly for watchOS now, so we can do it as an on-watch app instead of trusting Apple won't kill watchOS 1 style apps yet.