click on broadcast chat, go to game & move author was looking at

[schlawg]

We extend ui/chat with a callback mechanism that calls relay code on message submit. The relay callback provides a round id, game id, and move number that the chat system then embeds within some sentinel characters before sending to lila-ws.

Meanwhile in relayView, we add a click handler to each chat message div that parses the sentinel embedded string and loads the right game & move.