Add the ability to start and exec into a devcontainer (docker run -it)

[j2udev]

I would like to be able start and exec into my devcontainer with a single command (like you can with docker using docker run -it zsh for example).

So instead of:

devcontainer up

and

devcontainer exec --workspace-folder . zsh

There would be some alternative flag/command/whatever. It could maybe look something like:

devcontainer up -it --workspace-folder . zsh

As a side note, the --workspace-folder flag is a little unwieldy. It would be nice to at least have a shorthand.