Add Safari support 

> Update 2020
> 
> Apple plans to support WebExtensions in Safari starting from September 2020 with macOS Big Sur. These extensions will be published in the App Store. See https://developer.apple.com/videos/play/wwdc2020/10665/ for the announcement.

Source: https://stackoverflow.com/questions/47435082/will-safari-ever-support-webextensions-api