Add "unread" badges

[xobs]

Describe the problem

Unread message counts have become key featuers of modern chat programs, with everything from Slack to Discord to WhatsApp adding little badges to their icons to indicate when there are unread messages.

Cinny doesn't seem to yet have this feature, but it'd be nice if it did.

Describe the solution you'd like

I would like to have a list of unread messages on the program icon.

Alternatives considered

Alternatives include "Urgent" status, where the program gains a different colour on the dock. This would also work, though it provides less information.

Additional context

No response