Add paper link

Hi! Congrats on Xwin! It would be great to link the model to its paper on Daily Papers page.

README.md

@@ -195,3 +195,7 @@ Please consider citing our work if you use the data or code in this repo.
 ## Acknowledgements
 
 Thanks to [Llama 2](https://ai.meta.com/llama/), [FastChat](https://github.com/lm-sys/FastChat), and [vLLM](https://github.com/vllm-project/vllm).
+
+## Paper
+
+arxiv.org/abs/2405.20335