update paper link

README.md

@@ -21,5 +21,5 @@ pinned: false
 - Webpage: [evo-eval.github.io](https://evo-eval.github.io/)
 - Leaderboard: [evo-eval.github.io/leaderboard.html](https://evo-eval.github.io/leaderboard.html)
 - Visualization: [evo-eval.github.io/visualization.html](https://evo-eval.github.io/visualization.html)
-- Paper: TODO
+- Paper: [arXiv](https://arxiv.org/abs/2403.19114)
 - PyPI: [evoeval](https://pypi.org/project/evoeval/)