### 🚀 Feature add A2C algorithm in openrl ### Motivation _No response_ ### Pitch _No response_ ### Alternatives _No response_ ### Additional context _No response_ ### Checklist - [X] I have checked that there is no similar [issues](https://github.com/OpenRL-Lab/openrl/issues) in the repo - [X] I have read the [documentation](https://openrl-docs.readthedocs.io/)
🚀 Feature
add A2C algorithm in openrl
Motivation
No response
Pitch
No response
Alternatives
No response
Additional context
No response
Checklist