An Example for UDP Multicast

The code snippet here: https://docs.rs/async-std/1.1.0/async_std/net/struct.UdpSocket.html#method.join_multicast_v4 is a start, but as someone who has never used multicast before, I think a full example that does something like multicasting a given value every n seconds, while listening for packets from other multicasters could be very useful.