That is dictated by the browser, and not something that the extension can "workaround". You can read more about it here: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Content_scripts#restricted_domains but it is for security purposes. No Add-on can run on the Add-ons store page. The only workaround I can say would be to use a different browser (such as Chrome/Edge) with this extension installed (from their store), because they will allow extensions to run on this page since they can't support Firefox Add-ons. You can do that for reading through reviews and things, but to actually install it you'd need to be back in Firefox again, but it could be to just simply install the extension if you want it.