2 Requests: Overlay Fade & Interactive Animate Along Side

[littleowl]

In order to avoid overuse of PrimitiveNavigationTransition, it would be great to have two things:

1. An overlay transition that could be combined with other navigation transitions to accomplish similar results to the default transition, only customized.. (Bonus if we could define the overlay with SwiftUI view body builder.)
2. Add the possibility to animate alongside the transition, a State value, or view model property so that either the from-view or to-view can animate something in sync with the transition. Ideally, this could be interactive with either the edge pan or pan interactive modes.

Great Lib BTW!