PipeScript action should attempt discovery of email

When the PipeScript action sets committer info, it defaults to assuming an email of ```$GitUserName@github.com```

This should be automatically discovered where possible:

~~~PowerShell
Invoke-RestMethod -uri "https://api.github.com/user/emails" -Headers @{Authorization = "token $env:GITHUB_TOKEN"} |
    Select-Object -First 1 -ExpandProperty email
~~~