Using jax scan for PPO + atari + envpool XLA (#328)

jax.scan for ppo + atari + envpool and corresponding docs and tests

Author: 51616

README.md

@@ -122,6 +122,7 @@ You may also use a prebuilt development environment hosted in Gitpod:
 | |  [`ppo_atari_lstm.py`](https://github.com/vwxyzjn/cleanrl/blob/master/cleanrl/ppo_atari_lstm.py),   [docs](https://docs.cleanrl.dev/rl-algorithms/ppo/#ppo_atari_lstmpy)
 | |  [`ppo_atari_envpool.py`](https://github.com/vwxyzjn/cleanrl/blob/master/cleanrl/ppo_atari_envpool.py),   [docs](https://docs.cleanrl.dev/rl-algorithms/ppo/#ppo_atari_envpoolpy)
 | | [`ppo_atari_envpool_xla_jax.py`](https://github.com/vwxyzjn/cleanrl/blob/master/cleanrl/ppo_atari_envpool_xla_jax.py), [docs](/rl-algorithms/ppo/#ppo_atari_envpool_xla_jaxpy)
+| | [`ppo_atari_envpool_xla_jax_scan.py`](https://github.com/vwxyzjn/cleanrl/blob/master/cleanrl/ppo_atari_envpool_xla_jax_scan.py), [docs](/rl-algorithms/ppo/#ppo_atari_envpool_xla_jax_scanpy)
 | |  [`ppo_procgen.py`](https://github.com/vwxyzjn/cleanrl/blob/master/cleanrl/ppo_procgen.py),   [docs](https://docs.cleanrl.dev/rl-algorithms/ppo/#ppo_procgenpy)
 | |  [`ppo_atari_multigpu.py`](https://github.com/vwxyzjn/cleanrl/blob/master/cleanrl/ppo_atari_multigpu.py),  [docs](https://docs.cleanrl.dev/rl-algorithms/ppo/#ppo_atari_multigpupy)
 | | [`ppo_pettingzoo_ma_atari.py`](https://github.com/vwxyzjn/cleanrl/blob/master/cleanrl/ppo_pettingzoo_ma_atari.py),  [docs](https://docs.cleanrl.dev/rl-algorithms/ppo/#ppo_pettingzoo_ma_ataripy)

benchmark/ppo.sh

@@ -104,4 +104,10 @@ OMP_NUM_THREADS=1 xvfb-run -a poetry run python -m cleanrl_utils.benchmark \
     --command "poetry run python cleanrl/gymnasium_support/ppo_continuous_action.py --cuda False --track" \
     --num-seeds 3 \
     --workers 9
- 
+ 
+poetry install --with envpool,jax
+python -m cleanrl_utils.benchmark \
+    --env-ids Pong-v5 BeamRider-v5 Breakout-v5 \
+    --command "poetry run python cleanrl/ppo_atari_envpool_xla_jax_scan.py --track --capture-video" \
+    --num-seeds 3 \
+    --workers 1