[Build] revert site to webpack config (#3747)

docs/site/utils/i18n.js

@@ -0,0 +1,18 @@
+// component mixin
+import { get } from '../../../src/utils';
+import { camelize } from '../../../src/utils/format/string';
+
+export default {
+  computed: {
+    $t() {
+      const { name } = this.$options;
+      const prefix = name ? camelize(name) + '.' : '';
+      const messages = this.$vantMessages[this.$vantLang];
+
+      return (path, ...args) => {
+        const message = get(messages, prefix + path) || get(messages, path);
+        return typeof message === 'function' ? message(...args) : message;
+      };
+    }
+  }
+};