fix(flutter): 评论输入增加登录闸

lib/l10n/app_localizations_en.dart

@@ -448,6 +448,9 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get writeComment => 'Write a comment';
 
+  @override
+  String get commentLoginHint => 'Sign in to comment';
+
   @override
   String get postComment => 'Post';