Add pipeline tag

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

README.md

@@ -1,5 +1,8 @@
 ---
 license: apache-2.0
+pipeline_tag: image-to-video
+tags:
+- human-animation
 ---
 # StableAnimator