One person, one vote: building live voting with message annotations

Live polls are a staple of conferences, streams, and all-hands: a question goes up on the big screen, everyone votes from their phone, and the bars race each other in realtime. There’s a lot of different ways you could implement this. The most obvious way is a CRUD app backed by a server that votes are POSTed to, and the server keeps a running count. But this is the Ably blog, so we’re obviously g