Add pipeline tag

This PR adds the `pipeline_tag: text-retrieval` to the model card's metadata. This tag is crucial for discoverability on the Hugging Face Hub, allowing users to find this model when filtering for text retrieval tasks. It also helps categorize the model correctly given its function as a "Knowledgeable Passage Retriever" as described in the paper.

README.md

@@ -1,16 +1,16 @@
 ---
-tags:
-- transformers
-- sentence-transformers
+base_model:
+- bge-base-en-v1.5
 language:
 - en
-license: apache-2.0
 library_name: transformers
-base_model:
-- bge-base-en-v1.5
+license: apache-2.0
+tags:
+- transformers
+- sentence-transformers
 model_index:
 - name: kpr-bge-base-en-v1.5
-results:
+pipeline_tag: text-retrieval
 ---
 
 # Knowledgeable Embedding: kpr-bge-base-en-v1.5