Super love the fact that it's open-source. I suggest adding a key bind to open the popup so that the users don't have to scroll to the upper right to adjust the volume.
I'd love to but from what I understand that would require a background.js, which I didn't want to implement... As it requires additional permissions... see: https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/manifest.json/permissions#activetab_permission
