Have put it on my todo to add inverse so on is off.
url is any reachable web url. This can also be a file you copied manually into a custom www directory (you can add a shadow directory in server where you put your web files. I think I will add that for next release as well to be in storage directory so it gets easier.
You can not use a class name for a font. You need a separate svg file for that icon, which is normally also offered.
