Thanks for this great project! A quick feature request: [When loading models from the HuggingFace Hub](https://github.com/vllm-project/vllm/blob/7e90a2d11785b4cba5172f13178adb6d194a867f/vllm/config.py#L79), allow providing custom values to overwrite the default `config.json`. For example, change [the value of `max_position_embeddings` from `32768`](https://huggingface.co/mistralai/Mistral-7B-Instruct-v0.1/blob/7ad5799710574ba1c1d953eba3077af582f3a773/config.json#L11) to `100000`, to allow longer prompts.