add WorkoutStateManager for ViewModel functionality

WorkoutsPlus/Configuration/NavigationManager.swift

@@ -14,6 +14,20 @@ class NavigationManager: ObservableObject {
 				path = NavigationPath()
 				path.append(destination)
 		}
+		
+		func popToRoot() {
+				path = NavigationPath()
+		}
+		
+		func pop() {
+				if !path.isEmpty {
+						path.removeLast()
+				}
+		}
+		
+		func push(_ destination: NavigationDestination) {
+				path.append(destination)
+		}
 }
 
 enum NavigationDestination: Hashable {