I'm building a Firefox extension and was confused by what I can and cannot do with the WebExtensions API.
Basically what I'm trying to do is perform some CSS operation in the address bar of Firefox, for simplicity, say add an underline to the URL or make the base URL bold.
How can I do it with the WebExtensions API? I've seen the documentation and insertCSS is close, but does the same for the page not the addressbar.
Note that I'm not looking at Page Actions, but rather styling the text in the address bar itself.
Help much appreciated. :)