Add support for cohere models in Instructor

[lidiyam]

Is your feature request related to a problem? Please describe.
Add support for cohere models in Instructor

Describe the solution you'd like
Command-R and Command-R-plus models are finetuned for tool use and have the capabilities to produce structured JSON. It'd be great to include that into Instructor.

Describe alternatives you've considered
.from_litellm technically supports any hf model, but requires loading & inferencing 35B+ param models locally. It'd be nice to leverage cohere's /chat endpoint.

Additional context
I already have some working code to do this (heavily inspired by instructor's philosophy), just need to clean it up and merge it in here.