Add docs for plugin push

Signed-off-by: Anusha Ragunathan <anusha@docker.com>
Upstream-commit: f1598f8b82
Component: cli

components/cli/command/plugin/push.go

@@ -14,8 +14,8 @@ import (
 
 func newPushCommand(dockerCli *command.DockerCli) *cobra.Command {
 	cmd := &cobra.Command{
-		Use:   "push PLUGIN",
-		Short: "Push a plugin",
+		Use:   "push NAME[:TAG]",
+		Short: "Push a plugin to a registry",
 		Args:  cli.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			return runPush(dockerCli, args[0])