🐛 BUG: ESM Style config does not work

[dsheng3]

Quick checklist

• I am using the latest version of Snowpack and all plugins.

What package manager are you using?

npm

What operating system are you using?

Windows

Describe the bug

The ESM-style example config leads to an error. The CommonJS-Style, which is created by snowpack init works fine.

npm run start

leads to

export default {
^^^^^^

SyntaxError: Unexpected token 'export'
    at Object.compileFunction (node:vm:352:18)
    at wrapSafe (node:internal/modules/cjs/loader:1031:15)
    at Module._compile (node:internal/modules/cjs/loader:1065:27)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1153:10)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)
    at ModuleWrap.<anonymous> (node:internal/modules/esm/translators:190:29)
    at ModuleJob.run (node:internal/modules/esm/module_job:185:25)
    at async Promise.all (index 0)
    at async ESMLoader.import (node:internal/modules/esm/loader:281:24)

Steps to reproduce

1. Follow the getting-started guide https://www.snowpack.dev/tutorials/getting-started until npm run start ✅
2. Add ESM-style snowpack.config.js as in https://www.snowpack.dev/reference/configuration

// Example: snowpack.config.mjs
// The added "@type" comment will enable TypeScript type information via VSCode, etc.

/** @type {import("snowpack").SnowpackUserConfig } */
export default {
  plugins: [
    /* ... */
  ],
};

3. npm run start fails with error message Unexpected token 'export' ...
4. Expected: no error and same behavior as in step 1.

Link to minimal reproducible example (optional)

No response