can't build cocoascript in js file
src/my-command.js

```javascript
var writeTextToFile = function(text, filePath) {
  var t = [NSString stringWithFormat: @ "%@", text],
      f = [NSString stringWithFormat: @ "%@", filePath];
      return [t writeToFile: f atomically: true encoding: NSUTF8StringEncoding error: nil];
}

export default function(context) {

}
```

I can't build this  file in 'npm run start'

```javascript
error Error while building my-command.js
./src/my-command.js
Module build failed: SyntaxError: Unexpected token, expected , (3:22)
```
  
  