[Feature]: Allow custom prompt templates to be set for litellm proxy

The Feature

let user set custom prompt templates for litellm proxy

Motivation, pitch

user request

Twitter / LinkedIn details

No response

cc: @abhinavkulkarni

This is now live

litellm --config

opens up a model config - you can modify the model's specific prompt template and save it

We will read this whenever you run

litellm --model <your-model-name> .. 

again, for that model