events - add task

chapters/smart-contracts/lab/content/events.md

@@ -65,4 +65,7 @@ The structure of an event is:
 And when you want to emit an event, just call the function:
 ```rust
     self.the_function_you_call_when_you_want_to_emit_en_event(field1, field2, field3, field4);
-```
+```
+
+## Task
+Last time you interacted with the [ping-pong contract](https://github.com/multiversx/mx-ping-pong-sc). This time, you have to inspect the contract and call an endpoint that emits an event. Don't forget to check the logs!