docs: align custom-directive example with content (#3093)

docs:  align example description with content

src/guide/reusability/custom-directives.md

@@ -25,7 +25,7 @@ In addition to the default set of directives shipped in core (like `v-model` or
 
 We have introduced two forms of code reuse in Vue: [components](/guide/essentials/component-basics) and [composables](./composables). Components are the main building blocks, while composables are focused on reusing stateful logic. Custom directives, on the other hand, are mainly intended for reusing logic that involves low-level DOM access on plain elements.
 
-A custom directive is defined as an object containing lifecycle hooks similar to those of a component. The hooks receive the element the directive is bound to. Here is an example of a directive that focuses an input when the element is inserted into the DOM by Vue:
+A custom directive is defined as an object containing lifecycle hooks similar to those of a component. The hooks receive the element the directive is bound to. Here is an example of a directive that adds a class to an element when it is inserted into the DOM by Vue:
 
 <div class="composition-api">