[speech-to-text] Adding language identification model

[armin-rad-techlabs]

New model has been added to Watson Speech-to-text service which needs to be added to Node SDK.

1. the model end point is /v1/detect_language
2. optional parameter for the call is lid_confidence
3. response looks like this:

"results": [
      {
         "language_info": [
            {
               "confidence": 0.93,
               "language": "en",
               "timestamp": 1.76
            }
         ]
      },
      {
         "language_info": [
            {
               "confidence": 0.99,
               "language": "en",
               "timestamp": 2.28
            }
         ]
      }
]

More details on this model can be found here: https://cloud.ibm.com/docs/speech-to-text?topic=speech-to-text-speech-language-identification