This misses a test because Favcount doesn’t exposes a get to the counter.
Also, since this code deals with all possible notifications configs we support:
- favicon notification
- favicon new content
- title notification
- title new content
the code is a bit complicated to follow. We may look into refactoring it when a good opportunity arises, like if https://w3c.github.io/badging/ setClientBadge() method gives us a cleaner way to notify users.