Hi Dimka - we don't have a deep GitHub integration that works in this way currently - you can certainly checkout a github repo and reference a file from that checkout in your workspace.yaml, but I imagine you'll looking for something with less manual effort.
If you don't mind, could you share a bit more about what kind of configuration you're imagining you would need to set for this / are there are any other features in other systems that you're specifically thinking of when you mention this?