Indicate when there are no notifications

Use an icon / text to indicate that there are currently no notifications?

@snwh could you help here styling this? I think we want to use some background (so it will also work with transparent background as in the new mockups), dim the icon.

Also the icon itself from #744 (closed) looks confusing to me as it overlaps with the same icon we use for audio/led/haptic feedback so help here would be appreciated.

This is a prereq for some other work like !934 (merged) and #603 (closed) .