Add Sentence Transformers library_name

Hello!

## Preface
Congratulations on the release, I missed this when it was originally published! The scores look very impressive - do you want to share your rough training approach? I'm pretty curious.

## Details
I added the Sentence Transformers library_name, to make it easier for users to find this model when searching for a Sentence Transformers-compatible reranker here: https://huggingface.co/models?pipeline_tag=text-ranking&library=sentence-transformers&sort=trending

- Tom Aarsen

README.md

@@ -11,6 +11,7 @@ tags:
 - code
 - stem
 - medical
+library_name: sentence-transformers
 ---
 
 <img src="https://i.imgur.com/oxvhvQu.png"/>