add jupyterlab git

[proppy]

add https://github.com/jupyterlab/jupyterlab-git so that it's easier to version the notebooks

@joamatab

[proppy]

we could also have a dedicated cloud repository created inside the project, but I'm not sure how useful that would be given that teams are likely to already have some kind of source control inplace they want to interface with.

maybe just an empty repository that could make a new remote?