Support image upload option

[jadbox]

Vision is documented here: https://platform.openai.com/docs/guides/vision

[mme]

Unfortunately GPT Vision does not support function calls at the moment, which limits its usefulness in the context of Beak.js.

From the docs:

"Currently, GPT-4 with vision does not support the message.name parameter, functions/tools, response_format parameter, and we currently set a low max_tokens default which you can override."