Add Async image loading

Examples/Time Travel/SwiftUITimeTravel/TodoList/Model/TodoItem.swift

@@ -0,0 +1,7 @@
+import SwiftUI
+
+struct TodoItem: Identifiable {
+    var id: UUID
+    var title: String
+    var isFinished: Bool
+}

Examples/Time Travel/SwiftUITimeTravel/TodoList/Model/TodoState.swift

@@ -0,0 +1,39 @@
+import SwiftUI
+
+struct TodoState {
+    var isCreatingItem: Bool = false
+    var partialItemName: String = ""
+    var todoItems: [TodoItem] = []
+}
+
+extension TodoState: StateMachine {
+    
+    enum Event {
+        case startCreatingItem
+        case cancelCreatingItem
+        case changePartialItemName(String)
+        case addItem
+        case setItemDone(identifier: UUID, isDone: Bool)
+    }
+    
+    mutating func update(with event: TodoState.Event) {
+        switch event {
+        case .addItem:
+            todoItems.append(TodoItem(id: UUID(), title: partialItemName, isFinished: false))
+            partialItemName = ""
+            isCreatingItem = false
+        case .changePartialItemName(let name):
+            partialItemName = name
+        case .cancelCreatingItem:
+            isCreatingItem = false
+        case .startCreatingItem:
+            isCreatingItem = true
+            partialItemName = ""
+        case .setItemDone(let identifier, let isDone):
+            if let index = todoItems.firstIndex(where: { $0.id == identifier }) {
+                todoItems[index].isFinished = isDone
+            }
+        }
+    }
+    
+}