GitHub Red Alert

Changes the notification icon to red if you have participating notifications

As a GitHub user I pay very close attention to the Participating notification, i.e. the notifications you get from participating on a thread or being directly mentioned by others (by handle or team). Unfortunately just by looking at the notification bell, there's no way to distinguish if the notifications are participating or generally unread. Since I don't follow generic Unread notifications as closely as I do the Participating ones, I decided to augment the UI to distinguish the two.