[Help Wanted] Litellm integrate into ModelClient

[liyin2015]

Model Client: https://lightrag.sylph.ai/tutorials/model_client.html

LiteLLM: https://github.com/BerriAI/litellm

LiteLLM could enable users with many models used in the same format as openai. And it achieves so by using api requests instead of different provider's python SDKs. This can potentially end up with light dependencies given that they would work well, keep updated, and have no bugs.