derive Clone for Agent

This can be required when dealing with async code. I'm happy for you to
show me other ways if you think it's not necessary.

Signed-off-by: Maxime “pep” Buquet <pep@bouah.net>

src/lib.rs

@@ -345,6 +345,7 @@ impl ClientBuilder<'_> {
     }
 }
 
+#[derive(Clone)]
 pub struct Agent {
     sender_tx: mpsc::UnboundedSender<Packet>,
     default_nick: Rc<RefCell<String>>,