Add support for back navigation

Sources/Core/View/NavigationView.swift

@@ -34,7 +34,16 @@ public struct NavigationView<Item>: WinUIWidget where Item: NavigationViewItem {
     /// The currently selected item.
     var selectedItem: Selection {
         get {
-            if let last = path.last {
+            if let last = path.last(
+                where: { item in
+                    switch item {
+                    case .settings:
+                        return settings
+                    case let .custom(item):
+                        return items.contains(item)
+                    }
+                }
+            ) {
                 last
             } else if let first = items.first {
                 .custom(item: first)