chore(model gallery): add medgemma-4b-it

[mudler]

Description

This pull request adds a new entry for the MedGemma model family to the gallery/index.yaml file. MedGemma is a specialized AI model suite designed for medical text and image comprehension.

Additions to gallery/index.yaml:

New Model Entry: MedGemma

• Name: medgemma-4b-it
• Description: Introduced MedGemma, a collection of AI models optimized for healthcare applications. The description includes details about two variants:
  • MedGemma 4B: A multimodal model with a SigLIP image encoder, trained on diverse medical data like X-rays and histopathology slides. Available in pre-trained and instruction-tuned versions.
  • MedGemma 27B: A text-only model optimized for inference, available as an instruction-tuned version.
  • Both variants have been evaluated on clinical benchmarks and support fine-tuning for improved performance.
• URLs: Provided links to Hugging Face repositories hosting the models.
• Overrides: Added specific overrides for mmproj and model parameters.
• Files: Included file metadata (e.g., filenames, SHA-256 hashes, and URIs) for the model's GGUF format files. (F2b551e4L1528R152

Notes for Reviewers

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