Add pipeline tag

This PR ensures people can find the model at https://huggingface.co/models?pipeline_tag=image-to-video&sort=trending.

Cheers!

README.md

@@ -1,5 +1,6 @@
 ---
 license: apache-2.0
+pipeline_tag: image-to-video
 tags:
 - champ
 ---