Add pop-up when new announcement is made

[skoriop]

Right now, there is no indication of there being a new announcement.

Ideally we'd want to implement some actual read / unread stuff with an indicator on the announcements if we have time, but if not we should at least display an unread indicator permanently to make people check it.

Another similar thing is showing users a pop-up when there is a new announcement (then again, we definitely don't want to be displaying pop-ups every time without some read / unread logic).