Visually highlight own username when mentioned in the chat

[ollieparanoid]

Notifications on mentioning works now, thanks to using the serverside notification mechanism.
It would be nice if the own username was highlighted visually (i.e. in a different color, or with a background color or something) when mentioned. That way it would be easier to figure out where one was mentioned when scrolling through the backlog.

@mujx: thanks again for this great piece of software and for maintaining it so well 🎉