Add arXiv link

This PR adds a link to the arXiv paper.

README.md

@@ -13,3 +13,4 @@ tags:
 This dataset contains egocentric human-humanoid data that can be used to co-train manipulation policy for humanoid robot.
 
 For paper, visualization, and example code using this dataset, please refer to https://human-as-robot.github.io/
+arXiv link: https://arxiv.org/abs/2503.13441