Add pipeline tag

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

Let's make it top 1 trending :)

README.md

@@ -4,6 +4,7 @@ language:
 tags:
 - video
 license: "apache-2.0"
+pipeline_tag: text-to-video
 ---
 
 # Mochi 1 Preview