docs: Update vuepress example

Author: ktquez

docs/howto/vuepress.md

@@ -2,28 +2,28 @@
 
 In Vuepress the use and installation is also simple.
 
-```javascript
-// enhanceApp.js
-import VueDarkMode from '@vue-a11y/dark-mode'
-
-export default ({ Vue, isServer }) => {
-  if (!isServer) {
-    Vue.use(VueDarkMode)
-  }
-}
-```
-
 ::: warning
 VuePress applications are rendered by the server in Node.js when generating static builds. To avoid errors, we will wrap it inside the `<ClientOnly>` component.
 :::
 
-
 ```vue
-<ClientOnly>
-  <DarkMode>
-    <template v-slot="{ mode }">
-      Color mode: <span>{{ mode }}</span>
-    </template>
-  </DarkMode>
-</ClientOnly>
+<template>
+  <ClientOnly>
+    <DarkMode>
+      <template v-slot="{ mode }">
+        Color mode: <span>{{ mode }}</span>
+      </template>
+    </DarkMode>
+  </ClientOnly>
+</template>
+
+<script>
+import { DarkMode } from '@vue-a11y/dark-mode'
+
+export default {
+  components: {
+    DarkMode
+  }
+}
+</script>
 ```