feat: language setting

lib/main.dart

@@ -45,12 +45,15 @@ class _MainAppState extends State<MainApp> {
       SharedPrefSingleton().appTheme ? ThemeMode.light : ThemeMode.dark;
   ThemeMode get getCurrentTheme => _themeMode;
 
+  Locale? _locale;
+
   @override
   Widget build(BuildContext context) {
     return MaterialApp(
       theme: ThemeData(),
       darkTheme: ThemeData.dark(),
       themeMode: _themeMode,
+      locale: _locale,
       localizationsDelegates: AppLocalizations.localizationsDelegates,
       supportedLocales: AppLocalizations.supportedLocales,
       home: const Scaffold(
@@ -59,6 +62,12 @@ class _MainAppState extends State<MainApp> {
     );
   }
 
+  void changeLocale(Locale locale) {
+    setState(() {
+      _locale = locale;
+    });
+  }
+
   void changeTheme(ThemeMode mode) {
     mode == ThemeMode.light
         ? SharedPrefSingleton().setAppTheme(true).then((onValue) {