Support for commonjs exports.xxx?

Seems commonjs modules are not supported?

```js
module.exports.xxx = function () {
return 1
}
```
or
```js
exports.xxx = () => {
...
}

```

Is there a reason for this?

The issue names no files or tests. Start by reproducing both CommonJS examples through workerize-loader's webpack build path and inspect how module exports are handled. Done means both module.exports.xxx and exports.xxx forms work as shown, with their returned values available from the worker.

索引モデルが issue の本文から書いたものです。