title: Create GitHub actions that use powershell scripts
body: <p>I'd like to create a GitHub action that sets up an environment in Windows, running a few Powershell commands. Despite this can be done easily as a step, there does not seem to be a way to create a complete GitHub action for that. If I use this:</p>
  
  <pre><code>name: 'Rakudo Star fix for windows'
  description: 'Updates zef for RakudoStar'
  author: 'JJ'
  runs:
    using: 'node12'
    main: 'upgrade.ps1'
  </code></pre>
  
  <p>There does not seem a way to run anything other than a JS script, or even to declare the environment. I understand that's left for later, during the job steps, but anyway it looks like a hack. Is there anything I'm missing here?</p>