Citation for OpenRLHF in relation to the XTuner RLHF code and architecture

Hi, XTuner Team

Could you please add a citation for the source of the Ray+vLLM-based RLHF architecture - OpenRLHF, such as in the README.md file: https://github.com/InternLM/xtuner?tab=readme-ov-file#%EF%B8%8F-acknowledgement.
**We noticed that most RLHF-related code, particularly the Ray RLHF architecture in XTuner, are refactored from OpenRLHF.** According to the Apache License 2.0 of OpenRLHF, the original copyright statement must be included.

An example:
```
XTuner's RLHF solution mainly references OpenRLHF, for which we are grateful.
```

Related MR:
https://github.com/InternLM/xtuner/pull/736
https://github.com/InternLM/xtuner/pull/764

Thank you