build: add files of vant-cli 2

packages/vant-cli/src/compiler/compile-js.ts

@@ -0,0 +1,14 @@
+import { transformFileSync } from '@babel/core';
+import { removeSync, outputFileSync } from 'fs-extra';
+import { replaceExt } from '../common';
+
+export function compileJs(filePath: string) {
+  const result = transformFileSync(filePath);
+
+  if (result) {
+    const jsFilePath = replaceExt(filePath, '.js');
+
+    removeSync(filePath);
+    outputFileSync(jsFilePath, result.code);
+  }
+}