[auth] Enable translation for more languages

auth/lib/locale.dart

@@ -8,18 +8,25 @@ const List<Locale> appSupportedLocales = <Locale>[
   Locale('ar'),
   Locale('bg'),
   Locale('ca'),
+  Locale('cs'),
   Locale('de'),
   Locale('el'),
   Locale('en'),
   Locale('es', 'ES'),
   Locale('fa'),
   Locale('fr'),
+  Locale('hu'),
+  Locale('id'),
   Locale('it'),
   Locale('ja'),
+  Locale('ko'),
+  Locale('lt'),
   Locale('nl'),
   Locale('pl'),
+  Locale('pt'),
   Locale('pt', 'BR'),
   Locale('ru'),
+  Locale('sl'),
   Locale('sk'),
   Locale('tr'),
   Locale('uk'),

auth/lib/ui/settings/language_picker.dart

@@ -128,6 +128,8 @@ class _ItemsWidgetState extends State<ItemsWidget> {
         return 'العربية';
       case 'ca':
         return 'Català';
+      case 'cs':
+        return 'Čeština';
       case 'en':
         return 'English';
       case 'bg':
@@ -145,8 +147,14 @@ class _ItemsWidgetState extends State<ItemsWidget> {
         return 'Français';
       case 'de':
         return 'Deutsch';
+      case 'hu':
+        return 'Magyar';
+      case 'id':
+        return 'Bahasa Indonesia';
       case 'it':
         return 'Italiano';
+      case 'lt':
+        return 'Lietuvių';
       case 'nl':
         return 'Nederlands';
       case 'pl':
@@ -160,6 +168,8 @@ class _ItemsWidgetState extends State<ItemsWidget> {
         }
       case 'ru':
         return 'Русский';
+      case 'sl':
+        return 'Slovenščina';
       case 'sk':
         return 'Slovenčina';
       case 'tr':