docs: add missing import (#4389)

Author: nicolas-bastien

docs/en/guide/i18n.md

@@ -92,7 +92,7 @@ export default {
 <!-- docs/.vitepress/theme/Layout.vue -->
 <script setup lang="ts">
 import DefaultTheme from 'vitepress/theme'
-import { useData } from 'vitepress'
+import { useData, inBrowser } from 'vitepress'
 import { watchEffect } from 'vue'
 
 const { lang } = useData()