[docs][zh] updated config

docs/.vuepress/config.js

 module.exports = {
-  title: 'Vue Loader',
-  description: 'Webpack loader for single-file Vue components',
+  locales: {
+    '/': {
+      lang: 'en-US',
+      title: 'Vue Loader',
+      description: 'Webpack loader for single-file Vue components'
+    },
+    '/zh/': {
+      lang: 'zh-CN',
+      title: 'Vue Loader',
+      description: '处理 Vue 单文件组件的 Webpack loader'
+    }
+  },
   serviceWorker: true,
   theme: 'vue',
   themeConfig: {
     repo: 'vuejs/vue-loader',
     docsDir: 'docs',
-    nav: [
-      {
-        text: 'Guide',
-        link: '/guide/'
+    locales: {
+      '/': {
+        label: 'English',
+        selectText: 'Languages',
+        editLinkText: 'Edit this page on GitHub',
+        nav: [
+          {
+            text: 'Guide',
+            link: '/guide/'
+          },
+          {
+            text: 'SFC Spec',
+            link: '/spec.html'
+          },
+          {
+            text: 'Options Reference',
+            link: '/options.html'
+          },
+          {
+            text: 'Migrating from v14',
+            link: '/migrating.md'
+          }
+        ],
+        sidebar: [
+          '/',
+          '/guide/',
+          '/guide/asset-url',
+          '/guide/pre-processors',
+          '/guide/scoped-css',
+          '/guide/css-modules',
+          '/guide/hot-reload',
+          '/guide/functional',
+          '/guide/custom-blocks',
+          '/guide/extract-css',
+          '/guide/linting',
+          '/guide/testing'
+        ]
       },
-      {
-        text: 'SFC Spec',
-        link: '/spec.html'
-      },
-      {
-        text: 'Options Reference',
-        link: '/options.html'
-      },
-      {
-        text: 'Migrating from v14',
-        link: '/migrating.md'
+      '/zh/': {
+        label: '简体中文',
+        selectText: '选择语言',
+        editLinkText: '在 GitHub 上编辑此页',
+        nav: [
+          {
+            text: '指南',
+            link: '/zh/guide/'
+          },
+          {
+            text: '单文件组件规范',
+            link: '/zh/spec.html'
+          },
+          {
+            text: '选项手册',
+            link: '/zh/options.html'
+          },
+          {
+            text: '如何从 v14 迁移',
+            link: '/zh/migrating.md'
+          }
+        ],
+        sidebar: [
+          '/zh/',
+          '/zh/guide/',
+          '/zh/guide/asset-url',
+          '/zh/guide/pre-processors',
+          '/zh/guide/scoped-css',
+          '/zh/guide/css-modules',
+          '/zh/guide/hot-reload',
+          '/zh/guide/functional',
+          '/zh/guide/custom-blocks',
+          '/zh/guide/extract-css',
+          '/zh/guide/linting',
+          '/zh/guide/testing'
+        ]
       }
-    ],
-    sidebar: [
-      '/',
-      '/guide/',
-      '/guide/asset-url',
-      '/guide/pre-processors',
-      '/guide/scoped-css',
-      '/guide/css-modules',
-      '/guide/hot-reload',
-      '/guide/functional',
-      '/guide/custom-blocks',
-      '/guide/extract-css',
-      '/guide/linting',
-      '/guide/testing'
-    ]
+    }
   }
 }