adding some sync information from sharelatex.pasteur.fr <-> $HOME

Q: How to sync the project files to a local folder?
A1: (from Amine) https://github.com/Jorl17/sharelatex-git-integration-unofficial#quickstart-getting-started
A2: the sharelatex installed is the community version, not the commercial one, as a consequence it is missing the "git" sync feature which is $$. More details at https://github.com/overleaf/overleaf/wiki