fix(chat-example): set idle_connection_timeout

This one seems to have fallen through the cracks somehow. Without setting an idle connection timeout, the connection is immediately closed.

Related: #4837.

Pull-Request: #4840.

examples/chat/src/main.rs

@@ -76,6 +76,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
                 mdns::tokio::Behaviour::new(mdns::Config::default(), key.public().to_peer_id())?;
             Ok(MyBehaviour { gossipsub, mdns })
         })?
+        .with_swarm_config(|c| c.with_idle_connection_timeout(Duration::from_secs(60)))
         .build();
 
     // Create a Gossipsub topic