Add Cohere provider

[Bilalkamal]

Add Cohere Provider Support

Description

Added support for Cohere, to expand aisuite's provider options.

Changes Made

• Added Cohere provider implementation in providers/cohere_provider.py
• Added necessary environment variables for Cohere API authentication
• Implemented provider class following the convention CohereProvider
• Added type hints and documentation following project standards

Testing

• Tested provider initialization
• Verified API connection and authentication
• Tested chat completion functionality
• All existing tests pass

Environment Variables Added

CO_API_KEY=

Related Documentation

• Added Cohere to the list of supported providers in README.md

Checklist

• Code follows project style guidelines
• Updated documentation
• Pre-commit hooks pass

[ksolo]

Suggested change

	To use Cohere with `aisuite`, you’ll need an [Cohere account](https://cohere.com/). After logging in, go to the [API Keys](https://dashboard.cohere.com/api-keyss) section in your account settings, agree to the terms of service, connect your card, and generate a new key. Once you have your key, add it to your environment as follows:
	To use Cohere with `aisuite`, you’ll need an [Cohere account](https://cohere.com/). After logging in, go to the [API Keys](https://dashboard.cohere.com/api-keys) section in your account settings, agree to the terms of service, connect your card, and generate a new key. Once you have your key, add it to your environment as follows:

[ksolo]

Suggested change

	Install the `openai` Python client:
	Install the `cohere` Python client:

[ksolo]

Suggested change

	import aisuite as ai
	client = ai.Client()
	model_id = "command-r-plus-08-2024"
	messages=[
	{"role": "user", "content": "Hi, how are you?"}
	]
	response = client.chat(
	model=f"{model_id}",
	messages=messages,
	)
	print(response)
	import aisuite as ai
	client = ai.Client()
	provider = "cohere"
	model_id = "command-r-plus-08-2024"
	messages = [
	{"role": "user", "content": "Hi, how are you?"}
	]
	response = client.chat.completions.create(
	model=f"{provider}:{model_id}",
	messages=messages,
	)
	print(response.choices[0].message.content)

[ksolo]

Does this return an compliant response, as in response.choices[0].message.content would work?