Highlights for splits when new messages are sent

[brian6932]

So, I should explain my usecase a little, I primarily use tabs as split groups, with like-channels. Some of these channels really don't receive messages often, so I'd like to have their split headers change color (not to the same one as the selected split ofc) when new messages are detected, kind of like tabs, that way you could effectively have minimized splits (the size of their headers), and still get contexts from them, while not needing to have /mentions open in the same tab, great for space savings.