Add example showing an unintuitive situation

where `MappedNavigatableSource` instances can be created in `build()` methods, which would then be recreated (and thus loose all state) on higher-level rebuilds/hot reloads

example/lib/src/examples/example_selection_navigator.dart

@@ -1,6 +1,8 @@
 import 'package:fdr/fdr.dart';
 import 'package:fdr_example/src/examples/dynamic_pop_navigator.dart';
-import 'package:fdr_example/src/examples/hot_reloadable_navigator.dart';
+import 'package:fdr_example/src/examples/hot_reloadable_mapped_navigator.dart';
+import 'package:fdr_example/src/examples/hot_reloadable_stateful_navigator.dart';
+import 'package:fdr_example/src/examples/hot_reloadable_stateless_navigator.dart';
 import 'package:fdr_example/src/examples/list_detail_navigator.dart';
 import 'package:fdr_example/src/examples/overlay_portal_navigator.dart';
 import 'package:flutter/cupertino.dart';
@@ -29,7 +31,9 @@ class ExampleSelectionNavigator
         examples: {
           'List Detail': () => ListDetailNavigator(),
           'Dynamic back behavior': () => DynamicPopNavigator(),
-          'Stateful Navigator w/ hot reload': () => HotReloadableNavigator(),
+          'Stateful Navigator': () => HotReloadableStatefulNavigator(),
+          'Stateless Navigator': () => HotReloadableStatelessNavigator(),
+          'Mapped Navigator': () => HotReloadableMappedNavigator(),
           'Overlay Portal': () => OverlayPortalNavigator(),
         },
         onExampleSelect: (exampleFactory) => this.state = exampleFactory(),

example/lib/src/examples/hot_reloadable_mapped_navigator.dart

@@ -0,0 +1,39 @@
+import 'package:fdr/fdr.dart';
+import 'package:flutter/material.dart';
+
+class HotReloadableMappedNavigator extends StatelessNavigator {
+  @override
+  List<DeclarativeNavigatable> build() {
+    return [
+      MappedNavigatorDemo(),
+    ];
+  }
+}
+
+class MappedNavigatorDemo extends MappedNavigatableSource<int> {
+  MappedNavigatorDemo() : super(initialState: 0);
+
+  @override
+  List<DeclarativeNavigatable> build() {
+    return [
+      Scaffold(
+        appBar: AppBar(
+          title: const Text('Stateless Navigator'),
+        ),
+        body: Center(
+          child: Column(
+            children: [
+              Text('Count: $state'),
+              FilledButton(
+                onPressed: () {
+                  state++;
+                },
+                child: const Text('Increment'),
+              )
+            ],
+          ),
+        ),
+      ).page(onPop: null),
+    ];
+  }
+}

example/lib/src/examples/hot_reloadable_navigator.dart → example/lib/src/examples/hot_reloadable_stateful_navigator.dart

@@ -4,7 +4,7 @@ import 'package:fdr/fdr.dart';
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
 
-class HotReloadableNavigator extends StatelessNavigator {
+class HotReloadableStatefulNavigator extends StatelessNavigator {
   @override
   List<DeclarativeNavigatable> build() {
     return [

example/lib/src/examples/hot_reloadable_stateless_navigator.dart

@@ -0,0 +1,34 @@
+import 'package:fdr/fdr.dart';
+import 'package:flutter/material.dart';
+
+class HotReloadableStatelessNavigator extends StatelessNavigator {
+  @override
+  List<DeclarativeNavigatable> build() {
+    return [
+      StatelessNavigatorDemo(greeting: 'hello, world!'),
+    ];
+  }
+}
+
+class StatelessNavigatorDemo extends StatelessNavigator {
+  @visibleForTesting
+  StatelessNavigatorDemo({
+    required this.greeting,
+  });
+
+  final String greeting;
+
+  @override
+  List<DeclarativeNavigatable> build() {
+    return [
+      Scaffold(
+        appBar: AppBar(
+          title: const Text('Stateless Navigator'),
+        ),
+        body: Center(
+          child: Text(greeting),
+        ),
+      ).page(onPop: null),
+    ];
+  }
+}