We provide a more sound SwiftUI sample and also show how to add user settings to a SwiftUI app.
Also rename Preferences to Settings in across the documentation.
* Update Sparkle 2.x paths, migration notes, code signing XPC Services
* Rename 1.x and 2.x to 1 and 2 where appropriate
* Update app cast example to use edSignature and remove Test App zip
* Update copyright to include initial release year