Image finetuning

[albertodepaola]

What does this PR do?

Adds an image finetuning recipe for Llama 3.2 with torchtune. Focused on structured data extraction.

Feature/Issue validation/testing

Tested by running the FT and custom evaluation multiple times, checking result repeatability.
Details in the Readme: https://github.com/meta-llama/llama-cookbook/tree/image-finetuning/getting-started/finetuning/vision

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline,
  Pull Request section?
• Was this discussed/approved via a Github issue? Please add a link
  to it if that's the case.
• Did you make sure to update the documentation with your changes?
• Did you write any new necessary tests?

Thanks for contributing 🎉!