update citation

README.md

@@ -89,10 +89,11 @@ We provide several agents under `./submission/` directory,  which can be submitt
 Please cite our paper if you use our codes or our weights in your own work:
 
 ```
-@article{lin2023tizero,
+@inproceedings{lin2023tizero,
   title={TiZero: Mastering Multi-Agent Football with Curriculum Learning and Self-Play},
   author={Lin, Fanqi and Huang, Shiyu and Pearce, Tim and Chen, Wenze and Tu, Wei-Wei},
-  journal={arXiv preprint arXiv:2302.07515},
+  booktitle={Proceedings of the 2023 International Conference on Autonomous Agents and Multiagent Systems},
+  pages={67--76},
   year={2023}
 }
 ```