docs: updates the examples in README to use currently supported models

[calicube]

Summary

Fixes #260
The example code provided in the README uses a specific model version (anthropic:claude-3-5-sonnet-20240620) that has been deprecated by Anthropic as of August 2025. This causes a 404 Not Found error when users attempt to run the quickstart example.

Changes:

• Updated the models list in the example code to use the latest stable version: anthropic:claude-sonnet-4-5-20250929.

Root Cause

The specific timestamped version 20240620 has been retired from their active API endpoints, leading the Anthropic Python SDK to return a NotFoundError.

# The current error in the log:
anthropic.NotFoundError: Error code: 404 - {
    'type': 'error', 
    'error': {
        'type': 'not_found_error', 
        'message': 'model: claude-3-5-sonnet-20240620'
    }
}

Solution

Update the model strings to use sonnet 4.5 model to ensure the README remains functional for new users.

import aisuite as ai
client = ai.Client()

models = ["openai:gpt-4o", "anthropic:claude-sonnet-4-5-20250929"]

messages = [
    {"role": "system", "content": "Respond in Pirate English."},
    {"role": "user", "content": "Tell me a joke."},
]

for model in models:
    response = client.chat.completions.create(
        model=model,
        messages=messages,
        temperature=0.75
    )
    print(response.choices[0].message.content)