Add link for Custom Events lesson

Author: rahaug

src/guide/component-custom-events.md

@@ -2,6 +2,8 @@
 
 > This page assumes you've already read the [Components Basics](component-basics.md). Read that first if you are new to components.
 
+<div class="vueschool"><a href="https://vueschool.io/lessons/communication-between-components?friend=vuejs" target="_blank" rel="sponsored noopener" title="Learn how to work with custom events on Vue School">Learn how to work with custom events in a free Vue School lesson</a></div>
+
 ## Event Names
 
 Like components and props, event names provide an automatic case transformation. If you emit an event from the child component in camel case, you will be able to add a kebab-cased listener in the parent: