feat(cli): support switch lang

packages/vant-cli/site/desktop/App.vue

@@ -1,6 +1,11 @@
 <template>
   <div class="app">
-    <van-doc :lang="lang" :config="config" :simulator="simulator">
+    <van-doc
+      :lang="lang"
+      :config="config"
+      :simulator="simulator"
+      :lang-configs="langConfigs"
+    >
       <router-view />
     </van-doc>
   </div>
@@ -9,6 +14,7 @@
 <script>
 import VanDoc from './components';
 import { config } from 'site-desktop-shared';
+import { setLang } from '../common/locales';
 
 function getPublicPath() {
   const { site } = config.build || {};
@@ -37,16 +43,29 @@ export default {
       return lang || '';
     },
 
+    langConfigs() {
+      const { locales = {} } = config.site;
+      return Object.keys(locales).map(key => ({
+        lang: key,
+        label: locales[key].langLabel || ''
+      }));
+    },
+
     config() {
       const { locales } = config.site;
 
       if (locales) {
-        const { lang } = this.$route.meta;
-        return locales[lang];
+        return locales[this.lang];
       }
 
       return config.site;
     }
+  },
+
+  watch: {
+    lang(val) {
+      setLang(val);
+    }
   }
 };
 </script>