[jupyterhub] add execute time extension

jupyterhub/Dockerfile

@@ -32,6 +32,7 @@ RUN python${PYTHON_VERSION} -m pip --no-cache-dir install \
         jupyter-webrtc \
         ipyvolume \
         jupyter-threejs \
+        jupyterlab-execute-time \
     && \
     python${PYTHON_VERSION} -m jupyter labextension install @ryantam626/jupyterlab_code_formatter && \
     python${PYTHON_VERSION} -m pip --no-cache-dir install jupyterlab_code_formatter && \