Add key at top level to avoid React console warnings.
Add key at top level to avoid React console warnings.

Co-Authored-By: Saul Shanabrook <d56586a0dbb4647ee15c48bd46af59221bc4184c@gmail.com>
jupyter/jupyterlab,jupyter/jupyterlab,jupyter/jupyterlab,jupyter/jupyterlab,jupyter/jupyterlab