Allow redemption of room invitations in search bar

[mplorentz]

Right now users have to tap invitation links in another app or navigation into the Room management screen to redeem them. Let's support redeeming them if they are pasted into the search bars on the Discover or Your Network tabs. If a URL looks like a room invitation we can show an alert "This looks like a room invitation. Would you like to join {room name}?". (Bonus points if it works for pub invitations too)