Add `library_name: transformers` metadata

This PR adds the `library_name: transformers` metadata tag to the model card. This will enable the automated `transformers` code snippet and inference widget on the Hugging Face Hub, improving usability and discoverability for users. The model's `config.json` and `tokenizer_config.json` files provide clear evidence of its compatibility with the `transformers` library.

README.md

@@ -1,15 +1,17 @@
 ---
-license: apache-2.0
+base_model:
+- openai-community/gpt2
 datasets:
 - databricks/databricks-dolly-15k
 language:
 - en
+license: apache-2.0
 metrics:
 - rouge
-base_model:
-- openai-community/gpt2
 pipeline_tag: text-generation
+library_name: transformers
 ---
+
 # SFT-gpt2-120M
 
 [paper](https://arxiv.org/abs/2306.08543) | [code](https://github.com/microsoft/LMOps/tree/main/minillm)