Refactor dataset configuration in documentation and codebase

- Updated dataset configuration keys from `dataset_root` to `root` and `num_episodes` to `num_episodes_to_record` for consistency.
- Adjusted replay episode handling by renaming `episode` to `replay_episode`.
- Enhanced documentation
- added specific processor to transform from policy actions to delta actions

docs/source/hilserl_sim.mdx

@@ -107,10 +107,10 @@ To collect a dataset, set the mode to `record` whilst defining the repo_id and n
   },
   "dataset": {
     "repo_id": "username/sim_dataset",
-    "dataset_root": null,
+    "root": null,
     "task": "pick_cube",
-    "num_episodes": 10,
-    "episode": 0,
+    "num_episodes_to_record": 10,
+    "replay_episode": null,
     "push_to_hub": true
   },
   "mode": "record"