node : add language detection support (#3190)

node : add language detection support (#3190)

This commit add support for language detection in the Whisper Node.js
addon example. It also updates the node addon to return an object
instead of an array as the results.

The motivation for this change is to enable the inclusion of the
detected language in the result, in addition to the transcription
segments.

For example, when using the `detect_language` option, the result will
now be:
```console
{ language: 'en' }
```

And if the `language` option is set to "auto", it will also return:
```console
{
  language: 'en',
  transcription: [
    [
      '00:00:00.000',
      '00:00:07.600',
      ' And so my fellow Americans, ask not what your country can do for you,'
    ],
    [
      '00:00:07.600',
      '00:00:10.600',
      ' ask what you can do for your country.'
    ]
  ]
}
```