Update library name

It doesn't seem like the model is compatible with Transformers, so it replaces it by a dedicated "song-generation" library tag to the hub so that you can properly track downloads.

Will then open a PR similar to https://github.com/huggingface/huggingface.js/pull/1529

README.md

@@ -3,7 +3,7 @@ language:
 - en
 - zh
 pipeline_tag: text-to-audio
-library_name: transformers
+library_name: song-generation
 ---
 
 # SongGeneration