Install lab extensions

[diocas]

This ticket is to discuss which Jupyterlab extensions to install in our image. This installation should be done in the image that results from #1 .
Please add any extension you find relevant.

• Github/lab integration
  • Mentioned in the Users Workshop. But this extension does not allow commit'ing, only viewing, so we need to decide wether this is relevant or not
• jupyterlab-git
  • This seems to be the one that we want
• nbresuse / jupyterlab-system-monitor
  • There is a way to display only in the taskbar instead of using this extension... To be checked what is needed.