Enable use of Docker commands from inside the DevContainer

[petersellars]

At the moment we get an error when starting the container and trying to run any docker commands.

FInd a fix for this that works!

[petersellars]

These commands made it work from within the container

groupadd -g XXX$ docker
usermod -aG docker vscode

Look to find a way to automate this.

[petersellars]

Have put this in the Dockerfile and it works, but this hard codes it to the group that may differ across instances.

Should put this into the run args of the devcontainer.