Fix missing plural keys (#9084)

* Update i18n-tasks to feature-missing-plural-keys

* Fix pluralizations with missing keys in Arabic

Fix #8554

* Add i18n-tasks missing-plural-keys to CircleCI

.circleci/config.yml

@@ -175,6 +175,7 @@ jobs:
       - *attach_workspace
       - run: bundle exec i18n-tasks check-normalized
       - run: bundle exec i18n-tasks unused
+      - run: bundle exec i18n-tasks missing-plural-keys
 
 workflows:
   version: 2