Add gradio chatbot for openai webserver

[arkohut]

Follow the example of https://github.com/vllm-project/vllm/blob/main/examples/gradio_webserver.py I create a gradio webserver for openai api server.

Right now I find that OpenAI-compatible api server has more features than the default webserver and is much more popular. This script will create a chatbot to test the web server.

Here is a command example:

$ python chat.py -m '01ai/Yi-34B-Chat-4bits' --stop-token-ids 7

Running on local URL:  http://127.0.0.1:8001
Running on public URL: https://747eb488ee1e9155e4.gradio.live

This share link expires in 72 hours. For free permanent hosting and GPU upgrades, run `gradio deploy` from Terminal to deploy to Spaces (https://huggingface.co/spaces)

Here is the screenshot: