update readme

docs/README.md

@@ -138,7 +138,9 @@ address = {北京},
 isbn = {9787115584700},
 url = {https://github.com/datawhalechina/easy-rl}
 }
+```
 
+```bibtex
 @book{wang2022easyrl,
 title = {Easy RL: Reinforcement Learning Tutorial},
 publisher = {Posts & Telecom Press},
@@ -149,6 +151,7 @@ isbn = {9787115584700},
 url = {https://github.com/datawhalechina/easy-rl}
 }
 ```
+
 如果您需要转载该教程的内容，请注明出处：[https://github.com/datawhalechina/easy-rl](https://github.com/datawhalechina/easy-rl)。
 
 ## 致谢