docs: optimize time of page load

lib/components/menu/index.tsx

@@ -1,10 +1,33 @@
 import React, { useEffect, useState } from 'react'
+import { useRouter } from 'next/router'
 import MenuLinks from './menu-links'
 import MenuSticker from './menu-sticker'
+import { useConfigs } from 'lib/config-context'
 
 const Menu: React.FC<{}> = () => {
+  const router = useRouter()
+  const { isChinese } = useConfigs()
   const [showAfterRender, setShowAfterRender] = useState<boolean>(false)
   useEffect(() => setShowAfterRender(true), [])
+  useEffect(() => {
+    const prefetch = async () => {
+      const urls = isChinese ? [
+        '/zh-cn/guide/introduction',
+        '/zh-cn/components/text',
+        '/zh-cn/customization',
+      ] : [
+        '/en-us/guide/introduction',
+        '/en-us/components/text',
+        '/en-us/customization',
+      ]
+      await Promise.all(urls.map(async (url) => {
+        await router.prefetch(url)
+      }))
+    }
+    prefetch()
+      .then()
+      .catch(err => console.log(err))
+  }, [isChinese])
   
   if (!showAfterRender) return null
   return (