Brave takes first steps towards vertical tabs

Brave have been working on vertical tabs for a few months now. They recently merged the basic vertical tabs functionality into master and released the first Nightly build that can do vertical tabs yesterday.

Playing around with it, they are still obviously rough around the edges, but the basic implementation seems good, borrowing a bunch of the good decisions made in Edge. Some things like tab groups technically work, but are visually glitchy for now.