This PR adds a comprehensive model card for this RetNet model, which is part of the research presented in the paper "[A Systematic Analysis of Hybrid Linear Attention](https://huggingface.co/papers/2507.06457)".
The model card includes:
- Relevant metadata (`license`, `library_name`, `pipeline_tag`) to enhance discoverability on the Hugging Face Hub.
- Links to the associated paper, project page (collection), and GitHub repository for the Flash Linear Attention project.
- A clear description of the model and a usage example using the `transformers` library for text generation.
- The academic citation for the related works.
