Add visual document retrieval tag

This PR ensures your model can be found at https://huggingface.co/models?pipeline_tag=visual-document-retrieval&sort=trending.

README.md

@@ -2,6 +2,7 @@
 license: apache-2.0
 base_model:
 - OpenGVLab/InternVL2_5-2B
+pipeline_tag: visual-document-retrieval
 ---
 # IDMR-2B