Add pipeline tag

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

Btw, would be great to add language tags for the supported languages :)

README.md

@@ -1,3 +1,7 @@
+---
+pipeline_tag: image-text-to-text
+---
+
 The following is the code to run Pangea-7B using huggingface generate:
 ```
 # Assuming that you have text_input and image_path