Add pipeline tag

This PR ensures the model can be found at https://huggingface.co/models?pipeline_tag=image-text-to-text&sort=trending.

README.md

@@ -9,6 +9,7 @@ metrics:
 base_model:
 - microsoft/phi-1_5
 library_name: adapter-transformers
+pipeline_tag: image-text-to-text
 tags:
 - medical
 - colonoscopy