Add pipeline tag, library name, and link to code and paper

This PR improves the model card by:

- Adding the `pipeline_tag: question-answering` to better categorize the model.
- Specifying the `library_name: transformers` for clarity and discoverability.
- Linking to the paper and the Github repository.

This will improve the model's discoverability and usability on the Hugging Face Hub.

README.md

@@ -1,3 +1,9 @@
 ---
 license: apache-2.0
----
+pipeline_tag: question-answering
+library_name: transformers
+---
+
+This repository contains the model described in the paper [A Systematic Investigation of Distilling Large Language Models into Cross-Encoders for Passage Re-ranking](https://arxiv.org/abs/2405.07920).
+
+The code for training and evaluation can be found at https://github.com/webis-de/msmarco-llm-distillation.