ctr: Add sandbox flag to ctr run

Add a flag to be able to run a container in a given sandbox.

Signed-off-by: Danny Canter <danny@dcantah.dev>

cmd/ctr/commands/commands.go

@@ -141,6 +141,10 @@ var (
 			Usage: "Runtime name or absolute path to runtime binary",
 			Value: defaults.DefaultRuntime,
 		},
+		cli.StringFlag{
+			Name:  "sandbox",
+			Usage: "Create the container in the given sandbox",
+		},
 		cli.StringFlag{
 			Name:  "runtime-config-path",
 			Usage: "Optional runtime config path",