Add arXiv link (2606.13477) to paper reference and citation

README.md

@@ -118,4 +118,4 @@ articles subject to each article's individual license; molecular structures use
 [PubChem](https://pubchem.ncbi.nlm.nih.gov/) and
 [OPSIN](https://github.com/dan2097/opsin).
 
-If you use SupraBench, please cite the paper and the upstream data sources.
+If you use SupraBench, please cite the [paper](https://arxiv.org/abs/2606.13477) and the upstream data sources.