docs: fix typo in intro (testing-library#1067)

Author: patrady

docs/user-event/intro.mdx

@@ -21,7 +21,7 @@ with any framework as long as there is a DOM.
 ## Difference to `fireEvent`
 
 The built-in [`fireEvent`](dom-testing-library/api-events.mdx#fireevent) is a
-utility to easier dispatch events. It dispatches exactly the events you tell it
+utility to easily dispatch events. It dispatches exactly the events you tell it
 to and just those - even if those exact events never had been dispatched in a
 real interaction in a browser.