Add `library_name` to model card metadata
This PR improves the model card by adding the library_name: transformers metadata tag. This will enable the automatic display of a "how to use" widget on the model page, providing a convenient code snippet for users to get started with the model using the Hugging Face transformers library.
Evidence for transformers compatibility comes from the config.json file (model_type: olmo2, architectures: ["Olmo2ForCausalLM"], transformers_version: "4.52.4") and the GitHub README which instructs to install transformers with RePo.
No sample usage code snippet has been added as a direct Python inference example was not explicitly found in the provided GitHub README, adhering to the guideline of not making up code. The existing arXiv paper link and other content remain unchanged.