I attempted to use this addon w/ Firefox, but it didn't work. An issue was already posted here about the addon-signing problem, but I did some research and (I think) you can temporarily use unsigned addons on about:debugging. When trying to do that, it said that the addon was outdated. I went into the code (on my end) and edited install.rdf so that I listed the most recent version of Firefox as the compatible one, but it said that it had an invalid install manifest. After doing more research, I learned that install manifests like install.rdf are outdated and no longer used.
I don't have any experience with Firefox Extension developing, or with JavaScript, so my recommendation is to update the extension for Firefox.
I attempted to use this addon w/ Firefox, but it didn't work. An issue was already posted here about the addon-signing problem, but I did some research and (I think) you can temporarily use unsigned addons on about:debugging. When trying to do that, it said that the addon was outdated. I went into the code (on my end) and edited install.rdf so that I listed the most recent version of Firefox as the compatible one, but it said that it had an invalid install manifest. After doing more research, I learned that install manifests like install.rdf are outdated and no longer used.
I don't have any experience with Firefox Extension developing, or with JavaScript, so my recommendation is to update the extension for Firefox.