Add pipeline tag and library name

This PR adds the `pipeline_tag` and `library_name` to the model card metadata to improve discoverability and clarity. The `pipeline_tag` is set to `text-classification` reflecting the model's functionality. The `library_name` is set to `transformers` as indicated by the provided usage example.

README.md

@@ -2,6 +2,8 @@
 license: apache-2.0
 base_model:
 - Qwen/Qwen2.5-1.5B
+pipeline_tag: text-classification
+library_name: transformers
 ---
 
 ## Overview
@@ -98,4 +100,6 @@ print(f"Overall Prompt Classification => {'UNSAFE' if overall_label == 1 else 'S
       primaryClass={cs.CL},
       url={https://arxiv.org/abs/2502.05163}, 
 }
-```
+```
+
+Code: https://github.com/yihedeng9/DuoGuard