There are still lots of interface messages that are hardcoded in English (e.g. the home page). These should be moved to the i18n files, and so made translatable on TranslateWiki.

This task will involve finding all the English messages, moving them to i18n/en.json, and accessing them via e.g. the Twig msg function {{ msg('msg-name-here'). The i18n/qqq.json file will also need to be updated to include the new messages. Make sure to run composer test and npm run test before submitting a pull request.