Add instructions for running in GH CodeSpaces

[sorenbs]

It would be incredibly convenient if you could include instructions and a Docker Compose file to enable running these benchmarks in Github Code Spaces.

Would you accept a PR to do this?

[elprans]

The instructions are [here] (https://github.com/edgedb/imdbench/blob/master/DEVELOP.rst), though I don't think you'll be able to run this in Codespaces.