Please add en.js to the language folder

[gb5256]

Hello,
I noticed quite some errors from a missing en.js file which indeed is not part of the language folder bundled with this package.
Please take it from here:
https://imperavi.com/download/account/core/lang:en/

Thanks.

PS: some people here have told some users with this question to just add this file by hand to their vendor folder.
I would strongly disencourage to do that as with a possible composer-update you might loose this change. Best approach is that one of the admins of this package is updating it.