screen sharing

[colinsauze]

The workshop attendees need to be able to see the instructors screen. Traditionally at Carpentries workshops this is done using a data projector, but we might want to run in environments where a data projector isn't available. If we had some way to share the instructors screen to all participants then that could solve this.

Possible solutions:

1. shellshare, this shares everything typed on a terminal to a webpage. It should be possible to run this on a Pi (see https://github.com/vitorbaptista/shellshare for source code.)
2. Instructor works inside a VNC session running on the Pi or their own laptop. VNC can be set to allow a view only mode to share the screen with multiple viewers. Web based VNC clients are available (https://github.com/novnc/noVNC) so learners wouldn't need to install any software. This has the advantage of allowing the instructor to show anything, both webpages, terminals, jupyter notebooks etc.
3. Is there some way to view somebody else's Jupyter hub/lab screen? This means everything would have to be done inside Jupyter hub.