Rated 4 out of 5 stars

per Yurij Gagarin el oct. 30, 2009 · enllaç permanent

That's exactly what i needed. Even if it should not be compaible with version 2.x, it works fine! Just edit the install.rdf file inside the xpi and change the maxversion value
Don't give 5 stars; i'd give if the button would be automatically placed in the toolbar.

thx to the author