WIP: Support for highlighted tabs
I implemented the functionality for managing highlighted tabs, there are some things to improve, i.e. I've hardcoded the style change.
It's my first merge-request and I'm pretty satisfied with the result. I've tried to change as little as possible and instead working around with the functions already there.
I've tested it a lot but I'll love to use this branch during my normal browser session to test it in real world condition but I don't know how to do it.