Add "any-to-any" pipeline tag

We recently added support for https://huggingface.co/models?pipeline_tag=any-to-any, would be great to update all 4M models with this tag :)

Cheers,
Niels

README.md

@@ -1,4 +1,5 @@
 ---
+pipeline_tag: any-to-any
 license: apache-2.0
 library_name: transformers
 ---