Set up codespaces for easy development

[JamesPHoughton]

Set up a gh codespaces config to make it simple for students to develop without having to get their machines configured in a special way

Running notes

• Had trouble with default codespace running ubuntu 20.xx, we need 22.xx
• using the empirica base image as the image for the codespaces container (ghcr.io/empiricaly/empirica:build-v1.9.0)
• when we tried to run test suite, asked for library XVFB, libgobject
• ooops, cypress needs electron - maybe this won't work for actually developing