Update modelcard metadata to better reference `voicecraft` models

Better to set `voicecraft` as a library_name.
See https://github.com/jasonppy/VoiceCraft/pull/90 and https://github.com/huggingface/huggingface.js/pull/626 for more details.

README.md

@@ -1,12 +1,12 @@
 ---
+library_name: voicecraft
 tags:
 - Text-to-Speech
-- VoiceCraft
 - pytorch_model_hub_mixin
 - model_hub_mixin
 repo_url: https://github.com/jasonppy/VoiceCraft
 ---
 
-This model has been pushed to the Hub using ****:
-- Repo: https://github.com/jasonppy/VoiceCraft
+This model has been pushed to the Hub using VoiceCraft:
+- Library: https://github.com/jasonppy/VoiceCraft
 - Docs: [More Information Needed]