please consider building an installable XPI for Firefox so it can be installed from the 'releases' page (AMO appears to have taken the add-on down and i'd like to link to an installable file for users ...
Purge XUL, XPCOM support for addons (Firefox extensions, themes) Force "WebExtensions" only for addons development (WebExtensions technology are not a total a replacer, and are non-proper mature ...