Support finetuning (with Transformers)

[bagustris]

Nowadays, fine-tuning is more prominent in speech processing by taking advantage of other already trained models.
Current Nkululeko only used pre-trained model as feature extractor. It would be very useful if Nkululeko could do finetuning just in one command with a given INI config file (ref [1]).

Possible Solution
Either make finetuning as new key in [model] category (inside INI file) or create new module, e.g., nkululeko.finetuning.
required arguments: base_model (or from_model), push_to_hub (later?)
optional arguments: learning_rate, epochs, batch_size, etc (maybe use default first)

The biggest challenge may be to connect Nkululeko's own (CSV) dataset with Transformers [2], since Transformers finetuning only accept audio in HF Dataset format (just the format, no need to upload the dataset to the Hub).

[1] https://huggingface.co/learn/audio-course/en/chapter4/fine-tuning
[2] https://discuss.huggingface.co/t/loading-custom-audio-dataset-and-fine-tuning-model/8836/5

[felixbur]

agreed

[felixbur]

first version implemented: 0.85.0
only classification so far