Improve --help pages

[cdrage]

What would you like to be added?

Improve the --help pages to include an example on how to actually use the command.

▶ kompose convert --help
Convert a Docker Compose file

Usage:
  kompose convert [flags]

Kubernetes Flags:
  -c, --chart                    Create a Helm chart for converted objects
      --controller               Set the output controller ("deployment"|"daemonSet"|"replicationController")
      --service-group-mode       Group multiple service to create single workload by "label"("kompose.service.group") or "volume"(shared volumes)
      --service-group-name       Using with --service-group-mode=volume to specific a final service name for the group

Why is this needed?

Better documentation.

Improve the kompose convert --help command as well as the kompose --help command.