feat: can change theme

Author: KyoheiG3

examples/generator_example/generator_app/lib/main_catalog.dart

@@ -6,14 +6,27 @@ void main() {
   runApp(MyApp());
 }
 
-class MyApp extends StatelessWidget {
+class MyApp extends StatefulWidget {
+  @override
+  State<MyApp> createState() => _MyAppState();
+}
+
+class _MyAppState extends State<MyApp> {
+  var _isDark = false;
+  final controller = TextEditingController();
+
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
       title: 'Playbook Demo',
-      theme: ThemeData.light(),
+      theme: _isDark ? ThemeData.dark() : ThemeData.light(),
       home: PlaybookGallery(
-        title: 'Sample app',
+        title: 'Generator app',
+        searchTextController: controller,
+        checkeredColor: null,
+        onCustomActionPressed: () => setState(() {
+          _isDark = !_isDark;
+        }),
         playbook: playbook,
       ),
     );