[Build] use vue-cli to build site (#3734)

site/vue.config.js

@@ -0,0 +1,35 @@
+const path = require('path');
+
+module.exports = {
+  publicPath: process.env.NODE_ENV === 'production' ? '/vant/' : '/',
+  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'
+    }
+  },
+  chainWebpack: config => config.resolve.extensions.prepend('.md'),
+  configureWebpack: {
+    module: {
+      rules: [
+        {
+          test: /\.md$/,
+          use: ['vue-loader', '@vant/markdown-loader']
+        }
+      ]
+    }
+  },
+  css: {
+    loaderOptions: {
+      less: {
+        paths: [path.resolve(__dirname, '../node_modules')]
+      }
+    }
+  }
+};