Add library_name metadata tag

This PR ensures the "how to use" button appears on the top right (with a Diffusers code snippet), ensuring people know with which library the model is best compatible.

README.md

@@ -1,6 +1,7 @@
 ---
 license: apache-2.0
 pipeline_tag: any-to-any
+library_name: diffusers
 ---
 
 <div align="center">