New source file: config/locales/notifier/en.yml
This is a new file and is not yet integrated into translatewiki.net.
You're much too quick. It takes a while for us to add support. Real life, and such :)
I've reviewed the file, some changes were made, and I made a few changes too. Everything was synched into the master repo, and lo and behold!
Btw, Greek translation is missing! :P