I know there was an extension for firefox but you gave up on it. It is unfair that people who use Firefox get punished all because they don't want a ram hungry web browser as well as privacy (both not offered by chrome). The extension gives features that you basically pay for with the subscription but you lose out on all because of the browser you use. If you won't make one then make a way that firefox users don't lose out on any features.
Firefox now uses WebExtensions API which is compatible with Chrome's extension architecture. This means you can potentially port Chrome extensions to Firefox with relatively minimal modifications.