Provision for Multitask training
**Is your feature request related to a problem? Please describe.**
So while training a conformer model in an unsupervised fashion. I saw usage of two loss, i.e. contrastive loss and mlm loss. 

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So if i want to train the conformer model for ASR as well as language detection at the same time provided lang_ID/labels. and using to two losses. Multitasking 
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to thave the data like this
{audio_filepath:"English/audio/file1/path", "duration": 2.0, text: "Transcritpion in english ", "lang_id": "English"}
{audio_filepath:"English/audio/file2/path", "duration": 2.0, text: "Transcritpion in english ", "lang_id": "English"}
{audio_filepath:"English/audio/file3/path", "duration": 2.0, text: "Transcritpion in english ", "lang_id": "English"}
{audio_filepath:"Hindi/audio/file/path", "duration": 2.0, text: "Transcritpion in Hindi ", "lang_id": "Hindi"}
{audio_filepath:"Hindi/audio/file/path", "duration": 2.0, text: "Transcritpion in Hindi ", "lang_id": "Hindi"}
{audio_filepath:"Hindi/audio/file/path", "duration": 2.0, text: "Transcritpion in Hindi ", "lang_id": "Hindi"}
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Similarly here also two losses will be taken into account. one can be ctc and other can be cross entropy. can in decoding, if a file is given first 30sec is chunked on which it will first detect the language and then decode the transcription in the aforementioned  language 
@titu1994 @meghmak13 
