add unsubscribe to interactive example

src/benlink/client.py

@@ -109,10 +109,15 @@ def handle_event(event):
 
 await radio.connect()
 
-radio.register_event_handler(lambda x: print(f"Received event: {x}"))
+unsubscribe = radio.register_event_handler(lambda x: print(f"Received event: {x}\n"))
 
 # Change the channel on the radio a few times to generate some events
 
+unsubscribe() # Unsubscribe the event handler
+
+# Change the channel on the radio a few times to generate some events and
+# observe that the event handler is no longer called
+
 await radio.disconnect() # When you're done with your session disconnect nicely
 ```