Add gym-xiangqi to third party environment list (#2230)
Add gym-xiangqi to third party environment list (#2230)

* Add gym-xiangqi to env list

* Update description

Co-authored-by: J K Terry <fd470d697b6449d3a775e543147311841dbfe3da@gmail.com>
Farama-Foundation/Gymnasium,Farama-Foundation/Gymnasium