Readme: Link to unittest action

README.md

@@ -1,5 +1,5 @@
 # mbr 🔥
-![Main](https://github.com/ZurichNLP/mbr/workflows/unittest/badge.svg)
+[![Main](https://github.com/ZurichNLP/mbr/workflows/unittest/badge.svg)](https://github.com/ZurichNLP/mbr/actions/workflows/unittest.yml)
 [![PyPI](https://img.shields.io/pypi/v/mbr)](https://pypi.python.org/pypi/mbr/)
 
 **mbr** adds Sampling-based Minimum Bayes Risk decoding to [Hugging Face transformers](https://github.com/huggingface/transformers). Originally proposed by [Eikema & Aziz (2022)](https://aclanthology.org/2022.emnlp-main.754/), this technique is a risk-minimizing algorithm for generating text with a language model.