--attach in create command

### What is the problem you're trying to solve

Hi, `--attach` flag is in `docker create` but not in `nerdctl create`.

I'd like to contribute this change in nerdctl but I found `--attach` is not mentioned in `nerdctl create` documentation as "unimplemented flag". So before I make the change, just want to confirm that `--attach` is an expected feature in `nerdctl create` and there is no implicit reason of not having --attach in `nerdctl create` intentionally.

### Describe the solution you'd like

Support `--attach` in `nerdctl create`.

### Additional context

https://docs.docker.com/engine/reference/commandline/create/#options
https://github.com/containerd/nerdctl#whale-blue_square-nerdctl-create