Add support for the multilingual option which is available in faster-whisper

[snoesberger]

The faster-whisper multilingual option allows language detection to be performed on each segment. With the multilingual option enabled, you can get better transcription results if the language was incorrectly detected in the first place, or if the spoken language is switched in the audio.

So it would be nice to have a command line parameter to enable the `multilingual' parameter.