Update README.md

Author: quantumiracle

README.md

@@ -115,7 +115,7 @@ Since Tensorflow 2.0 has already incorporated the dynamic graph construction ins
 
  * **QMIX**:
 
-     `qmix.py`: a multi-agent RL algorithm, demo environment using [pettingzoo](https://www.pettingzoo.ml/atari/entombed_cooperative).
+     `qmix.py`: a fully cooperative multi-agent RL algorithm, demo environment using [pettingzoo](https://www.pettingzoo.ml/atari/entombed_cooperative).
 
      paper: http://proceedings.mlr.press/v80/rashid18a.html