Docs: add English language support (#170)

* feat: support lang entry build

* feat: vant support lang switch

* move lang iframe-router to utils & fix router link bug

* add en-US config && add some translation

* chang async. to async_ (support superman cdn)

* add layout translation

* change nav style

* upgrade zan-doc

* fix: doc config

* upgrade zan-doc && remove useless code

* fix changelog generate path

build/webpack.config.prod.js

@@ -9,7 +9,7 @@ module.exports = merge(devConfig, {
     publicPath: 'https://b.yzcdn.cn/zanui/vue/',
     filename: '[name].[hash:8].js',
     umdNamedDefine: true,
-    chunkFilename: 'async.[name].[chunkhash:8].js'
+    chunkFilename: 'async_[name].[chunkhash:8].js'
   },
   devtool: false,
   plugins: [