Implement `message_to_anthropic_message` for `UserImageMessage`

[mentatbot[bot]]

This commit adds support for converting UserImageMessage to the Anthropic message format. The implementation mirrors the existing message_to_openai_message function, ensuring compatibility with image messages for Anthropic models.

Changes include:

• Added a new function to handle UserImageMessage in anthropic_chat_model.py.
• Updated vision.py to register the new function and ensure proper role assignment.

This enhancement allows the use of image messages with Anthropic models, similar to the existing support for OpenAI models.

Closes #3

[rawwerks]

@mentatbot - you didn't implement the API call correctly in "message_to_anthropic_message.register(UserImageMessage)"

here are two examples

import anthropic

client = anthropic.Anthropic()
message = client.messages.create(
    model="claude-3-5-sonnet-20240620",
    max_tokens=1024,
    messages=[
        {
            "role": "user",
            "content": [
                {
                    "type": "image",
                    "source": {
                        "type": "base64",
                        "media_type": image1_media_type,
                        "data": image1_data,
                    },
                },
                {
                    "type": "text",
                    "text": "Describe this image."
                }
            ],
        }
    ],
)
print(message)

message = client.messages.create(
    model="claude-3-5-sonnet-20240620",
    max_tokens=1024,
    system="Respond only in Spanish.",
    messages=[
        {
            "role": "user",
            "content": [
                {
                    "type": "text",
                    "text": "Image 1:"
                },
                {
                    "type": "image",
                    "source": {
                        "type": "base64",
                        "media_type": image1_media_type,
                        "data": image1_data,
                    },
                },
                {
                    "type": "text",
                    "text": "Image 2:"
                },
                {
                    "type": "image",
                    "source": {
                        "type": "base64",
                        "media_type": image2_media_type,
                        "data": image2_data,
                    },
                },
                {
                    "type": "text",
                    "text": "How are these images different?"
                }
            ],
        }
    ],
)