Project: vite
Task (challenging): Implement dynamical generation of in-memory virtual modules as a vite plugin.

For example:

src/files/a.ts
```js
export default 'a'
```

src/files/b.ts
```js
export default 'b'
```

src/index.js
```js
import files from '~files'
files.a.default // should be 'a'
files.b.default // should be 'b'
```

You can hardcode `src/files` and `~files` as a builtin rule when implementing this.

Besides this
- Add `import files from '~files'` in `src/index.js`
- Display JSON stringified files(without any whitespaces) in `src/index.js`