docs(api): add useRequestHeaders composable example (#8833)

Co-authored-by: Daniel Roe <daniel@roe.dev>

docs/content/3.api/1.composables/use-request-headers.md

@@ -5,7 +5,7 @@ description: "Use useRequestHeaders to access the incoming request headers."
 
 # `useRequestHeaders`
 
-Within your pages, components, and plugins you can use `useRequestHeaders` to access the incoming request headers.
+You can use built-in `useRequestHeaders` composable to access the incoming request headers within your pages, components, and plugins.
 
 ```js
 // Get all request headers
@@ -18,3 +18,21 @@ const headers = useRequestHeaders(['cookie'])
 ::alert{icon=👉}
 In the browser, `useRequestHeaders` will return an empty object.
 ::
+
+## Example
+
+We can use `useRequestHeaders` to access and proxy the initial request's `authorization` header to any future internal requests during SSR.
+
+The example below adds the `authorization` request header to an isomorphic `$fetch` call.
+
+```vue [pages/some-page.vue]
+<script setup>
+const { data } = await useFetch('/api/confidential', {
+  headers: useRequestHeaders(['authorization'])
+})
+</script>
+```
+
+::alert{icon=👉}
+[Another example](/getting-started/data-fetching#example-pass-client-headers-to-the-api) shows how we can pass cookies from the initial request to another API route.
+::