Was working and now not anymore for me. I've seen that some other people said that it's still working for them but not on my end. I'm not complaining but just to let you know it's not working for some people. Hope that you'll take a look into it. I'm on Firefox Nightly 61, even with a new fresh profile with no add-on other than this, it's not working.
Anyway thank you for the add-on!