irc: Add QUIT handling

This closes the connection if the client sends quit

In particular it allows irssi to exit quickly on /quit as it waits for
servers to close connections

(added in the middle to not causes conflicts with other in flight PRs,
might want to reorder these alphabetically or something later)

Author: martinetd

src/ircd/proto.rs

@@ -222,6 +222,10 @@ pub async fn ircd_sync_read(
                     }
                 }
             }
+            Command::QUIT(msg) => {
+                info!("QUIT {}", msg.unwrap_or_default());
+                break;
+            }
             Command::ChannelMODE(chan, modes) if modes.is_empty() => {
                 if let Err(e) = matrirc
                     .irc()