Add Translation support

Created MR, and added a patch in the meantime.

Are you sure this is the correct way to add translation support?
I have not done much in the way of translation in the past so am not sure.

It does seem though that you are translating the value as well as what is displayed to the user, which I don't think is desirable.
Also PHPCS outputs a warning "Only string literals should be passed to t() where possible"