jupyter lab fixes (#1139) [skip ci]

* add a basic notebook for lab users in the root

* update notebook and fix cors for jupyter

* cell is code

* fix eval batch size check

* remove intro notebook

scripts/cloud-entrypoint.sh

@@ -33,7 +33,7 @@ fi
 
 if [ "$JUPYTER_DISABLE" != "1" ]; then
     # Run Jupyter Lab in the background
-    jupyter lab --allow-root --ip 0.0.0.0 &
+    jupyter lab --port=8888 --ip=* --allow-root --ServerApp.allow_origin=* --ServerApp.preferred_dir=/workspace &
 fi
 
 # Execute the passed arguments (CMD)