[Build] enable site pwa (#3736)

site/vue.config.js

@@ -2,17 +2,10 @@ const path = require('path');
 
 module.exports = {
   publicPath: process.env.NODE_ENV === 'production' ? '/vant/' : '/',
+  productionSourceMap: false,
   pages: {
-    index: {
-      entry: 'src/desktop/main.js',
-      template: 'public/index.html',
-      filename: 'index.html'
-    },
-    mobile: {
-      entry: 'src/mobile/main.js',
-      template: 'public/index.html',
-      filename: 'mobile.html'
-    }
+    index: 'src/desktop/main.js',
+    mobile: 'src/mobile/main.js'
   },
   chainWebpack: config => config.resolve.extensions.prepend('.md'),
   configureWebpack: {