Show up usage information the right way

[jamesgeorge007]

Fixes #349

Fixed the usage information that showed up with --help which was misleading previously.

vsce --help shows:-

Usage: vsce <command> [options]

Options:
  -V, --version                        output the version number
  -h, --help                           output usage information

Commands:
  ls [options]                         Lists all the files that will be published
  package [options]                    Packages an extension
  publish [options] [<version>]        Publishes an extension
  unpublish [options] [<extensionid>]  Unpublishes an extension. Example extension id: microsoft.csharp.
  ls-publishers                        List all known publishers
  create-publisher <publisher>         Creates a new publisher
  delete-publisher <publisher>         Deletes a publisher
  login <publisher>                    Add a publisher to the known publishers list
  logout <publisher>                   Remove a publisher from the known publishers list
  show [options] <extensionid>         Show extension metadata
  search [options] <text>              search extension gallery

[jamesgeorge007]

@joaomoreno Thoughts 🤔

[joaomoreno]

Thanks! 🍻