feat(transformer): transformer-based backend

[mudler]

Is your feature request related to a problem? Please describe.
It makes sense to have a backend which is tied to https://github.com/huggingface/transformers. This would increase the range of support for LLM that LocalAI already offers

Describe the solution you'd like
Ideally would be preferred to use a wrapper around transformers and xformers to avoid duplicating efforts.

Describe alternatives you've considered

Additional context

[yhyu13]

Is Vllm fully integrated? vLLM begins to seem to be many AWQ quantized model's first choice recently

[mudler]

Is Vllm fully integrated? vLLM begins to seem to be many AWQ quantized model's first choice recently

yep, going into the next release soon!