[Doc] PPO Tutorial (#913)

Author: vmoens

docs/requirements.txt

@@ -16,7 +16,6 @@ functorch
 gym[classic_control]
 torchvision
 dm_control
-gym
 atari-py
 ale-py
 gym[accept-rom-license]

docs/source/_static/img/invpendulum.gif

@@ -30,14 +30,32 @@ TorchRL aims at a high modularity and good runtime performance.
 Tutorials
 =========
 
+Basics
+------
+
 .. toctree::
    :maxdepth: 2
 
    tutorials/torchrl_demo
-   tutorials/pretrained_models
+   tutorials/coding_ppo
    tutorials/tensordict_tutorial
    tutorials/tensordict_module
+
+Intermediate
+------------
+
+.. toctree::
+   :maxdepth: 2
+
    tutorials/torch_envs
+   tutorials/pretrained_models
+
+Advanced
+--------
+
+.. toctree::
+   :maxdepth: 2
+
    tutorials/multi_task
    tutorials/coding_ddpg
    tutorials/coding_dqn