Added Git-Extension

minimal/Dockerfile.2021-ss.1

@@ -34,6 +34,7 @@ RUN jupyter labextension install \
 	@jupyterlab/hub-extension \
 	@jupyterlab/toc-extension \
 	@jupyter-widgets/jupyterlab-manager \
+	@jupyterlab/git \
 	jupyter-matplotlib \
 	git+https://github.com/youngthejames/jupyterlab_filetree \
 	jupyterlab_iframe