docs: update count example (#743)

docs/content/3.docs/1.usage/1.data-fetching.md

@@ -24,18 +24,21 @@ Under the hood, `defer: false` uses `<Suspense>` to block the loading of the rou
 
 ### Example
 
-```js [server/api/index.ts]
+```js [server/api/count.ts]
 let counter = 0
-export default () => ++counter
+export default () => {
+  counter++
+  return JSON.stringify(counter)
+}
 ```
 
 ```vue [pages/index.vue]
 <script setup>
-const { data } = await useAsyncData('time', () => $fetch('/api/count'))
+const { data } = await useAsyncData('count', () => $fetch('/api/count'))
 </script>
 
 <template>
-  Page visits: {{ data.count }}
+  Page visits: {{ data }}
 </template>
 ```