Notifications: Separate out new following users

Current behavior: In the Notifications, the Updates category shows various things like new models and also new users who follow you.

Suggestion: Separate out the new users who follow you into a new category. It could be called Followers or Social (if there are more notifications to include in that category).

Reason: When a user follows me, I want to check out their profile to see if we have similar interests. I may follow them back.