docs(app): update

docs/content/3.components/0.app.md

@@ -9,7 +9,21 @@ links:
 
 ## Usage
 
-## Examples
+Wrap your app with this component in your `app.vue` to provide global configurations and enable features like toasts, tooltips, etc. as well as programmatic modals and slideovers.
+
+```vue [app.vue]
+<template>
+  <UApp>
+    <NuxtPage />
+  </UApp>
+</template>
+```
+
+It's using Radix Vue's [ConfigProvider](https://www.radix-vue.com/utilities/config-provider.html) to provide global configuration to all components:
+
+- Enables all primitives to inherit global reading direction.
+- Enables changing the behavior of scroll body when setting body lock.
+- Much more controls to prevent layout shifts.
 
 ## API