Add `library_name: comet`

This PR adds the `comet` library tag to this model such that e.g. the downloads can be tracked.
For more context see: https://github.com/huggingface/huggingface.js/pull/1219

README.md

@@ -1,5 +1,6 @@
 ---
 pipeline_tag: translation
+library_name: comet
 language:
 - multilingual
 - af