There is a new translator, which needs a new addon: DeepL
I fully agree with this.
There is already a brand-new Add-On:
But doesn’t look nice at the moment:
There are no synonyms just the rare translated word and no Design. There is much to do.
Edit: Synonyms added (21.11.2017)
Hello, I made a different one : https://addons.mozilla.org/fr/firefox/addon/deeplt/