Rated 3 out of 5 stars

by Firefox user 6913e1 on Nov. 17, 2017 ·

November 2017

was great but does not work anymore with Firefox 57

WARNING:
do not upgrade Firefox to version 57 or this add-on (and many others) will not work anymore!

by Oleksandr (Developer) on Nov. 17, 2017 ·

Unfortunately, WebExtensions (the new API for Firefox 57+) does not have the functionality for the correct operation of this addon in Firefox.

But you can install Firefox 52 ESR and enjoy work until June 2018
https://www.mozilla.org/en-US/firefox/organizations/faq/