Add ability to send images to LLMs

[dghirardo]

Hi @andreibondarev, I noticed that the current version already supports sending images to LLMs.

You just need to include the image within the messages parameter. For example, when using OpenAI models, you can include images using the image_url content type. Here's how:

llm = Langchain::LLM::OpenAI.new(api_key: ENV["OPENAI_API_KEY"])

llm.chat(
  messages: [
    {
      role: "user",
      content: [
        { type: "text", text: "What's in this image?" },
        {
          type: "image_url",
          image_url: {
            url: "https://upload.wikimedia.org/wikipedia/commons/thumb/d/dd/Gfp-wisconsin-madison-the-nature-boardwalk.jpg/2560px-Gfp-wisconsin-madison-the-nature-boardwalk.jpg"
          }
        }
      ]
    }
  ],
  model: "gpt-4o"
).completion

Other LLMs only support sending the image in base64 format, but this must still be done within the messages parameter.