Update base_model guidance: base_model can be an array (#1168)
* Update base_model example to make an array
* Add support for specifying multiple base models in model card metadata
* clarity fix
* Update base_model field in model card metadata
* make single ID
* Update docs/hub/model-cards.md
Co-authored-by: Pedro Cuenca <pedro@huggingface.co>
* Update docs/hub/model-cards.md
Co-authored-by: Pedro Cuenca <pedro@huggingface.co>
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Co-authored-by: Pedro Cuenca <pedro@huggingface.co>
