Add Async image loading

Examples/Time Travel/SwiftUITimeTravel/TimeTravelView/StateMachine.swift

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+/// Conforming types serve as the state of a time travelable application
+public protocol StateMachine {
+    
+    /// Events define things that can happen within your application that change its state.
+    ///
+    /// This might include things like text editing, button taps, or network responses.
+    associatedtype Event
+    
+    /// Applies an event to the current state.
+    mutating func update(with event: Event)
+}