Removed examples from import path in port_datasets

removed readme from droid examples and add a tutorial in docs

docs/source/_toctree.yml

@@ -17,6 +17,8 @@
     title: Train a Robot with RL
   - local: hilserl_sim
     title: Train RL in Simulation
+  - local: porting_datasets_v3
+    title: Porting Large Datasets
   title: "Tutorials"
 - sections:
   - local: smolvla