Add URL of published arXiv paper.

README.md

@@ -154,6 +154,7 @@ source images and release KamonBench solely for non-commercial research use.
   title  = {KamonBench: A Grammar-Based Dataset for Evaluating Compositional Factor Recovery in Vision-Language Models},
   author = {Sproat, Richard and Peluchetti, Stefano},
   year   = {2026},
+  url    = {https://arxiv.org/abs/2605.13322},
   note   = {arXiv preprint},
 }
 ```