The Firefox extension shouldn't be provided by extensions.gnome.org
Problem
Mozilla doesn't recommend installing extensions outside the Firefox Add-ons website. Plus, this can be a little concerning for users that never used extensions.gnome.org.
Proposed
Provide the Firefox browser extension through the Add-ons website[1]. That's already the case when using Chrome: the extension installation link is pointing to the Chrome Web Store.
[1] The extension is already available there, but it doesn't seem to be official, because the author isn't labeled as GNOME.
Edited by Ghost User