Tutorial : a better explanation of component events (#4639)

* feat(tutorial): better explanation of component events

Co-Authored-By: Antony Jones <ant@enzy.org>

Author: MeuhMeuh

site/content/tutorial/05-events/04-component-events/text.md

@@ -18,4 +18,10 @@ Components can also dispatch events. To do so, they must create an event dispatc
 </script>
 ```
 
-> `createEventDispatcher` must be called when the component is first instantiated — you can't do it later inside e.g. a `setTimeout` callback. This links `dispatch` to the component instance.
+> `createEventDispatcher` must be called when the component is first instantiated — you can't do it later inside e.g. a `setTimeout` callback. This links `dispatch` to the component instance.
+
+Notice that the `App` component is listening to the messages dispatched by `Inner` component thanks to the `on:message` directive. This directive is an attribute prefixed with `on:` followed by the event name that we are dispatching (in this case, `message`).
+
+Without this attribute, messages would still be dispatched, but the App would not react to it. You can try removing the `on:message` attribute and pressing the button again.
+
+> You can also try changing the event name to something else. For instance, change `dispatch('message')` to `dispatch('myevent')` in `Inner.svelte` and change the attribute name from `on:message` to `on:myevent` in the `App.svelte` component.