Add support for multiple image files in CreateImageEditRequest

[spantaleev]

Fixes #363

[64bit]

Thank you for the PR!

This can be improved to match the spec image string or array Required
https://github.com/openai/openai-openapi/blob/master/openapi.yaml#L21129-L21137

That's because a user can input a single or multiple images in builder like:

single image

  CreateImageEditRequestArgs::default()
     .image(single_image)
     ...
    .build()?

multiple image

  CreateImageEditRequestArgs::default()
     .image([image1, image2])  # this can be vector, or just [] 
     ...
    .build()?

There are pattern in the repo which makes it happen in other places, and then implement From traits to have API like above.