v2.0.0

Version 2 is here, with a bunch of new features:

• A new NSDocumentGroup Scene, which allows the use of a SwiftUI Window with NSDocument. This is offered as an alternative to the built-in DocumentGroup.
• A way to open SwiftUI Windows and Settings from anywhere in the app, not only from SwiftUI Views.
• An environment Scene modifier to pass an Environment value to multiple Scenes at once. This works the same as the environment View modifier.