docs: add api req helpers example (#2726)

docs/content/3.docs/2.directory-structure/12.server.md

@@ -49,6 +49,22 @@ export default async (req: IncomingMessage, res: ServerResponse) => {
 }
 ```
 
+#### Accessing req data
+
+```js
+import { useBody, useCookies, useQuery } from 'h3'
+
+export default async (req, res) => {
+  const query = await useQuery(req)
+  const body = await useBody(req) // only for POST request
+  const cookies = useCookies(req)
+  
+  return { query, body, cookies }
+}
+```
+
+Learn more about [h3 methods](https://www.jsdocs.io/package/h3#package-index-functions).
+
 ## Server Middleware
 
 Nuxt will automatically read in any files in the `~/server/middleware` to create server middleware for your project.