l10n: Enable persian language

lib/locale.dart

@@ -10,6 +10,7 @@ const List<Locale> appSupportedLocales = <Locale>[
   Locale('es', 'ES'),
   Locale('fr'),
   Locale('nl'),
+  Locale('fa'),
   Locale('pt', 'BR'),
   Locale('ru'),
   Locale("zh", "CN"),

lib/ui/settings/language_picker.dart

@@ -164,6 +164,8 @@ class _ItemsWidgetState extends State<ItemsWidget> {
         return '한국어';
       case 'ar':
         return 'العربية';
+      case 'fa':
+        return 'فارسی';
       default:
         return locale.languageCode;
     }