Allow uploading to Draft releases

[hayd]

Currently action exits without upload:

This is a draft-release, so we will do nothing"

I would actually like to see the attachments on the draft (before publish).
Perhaps this could be a configuration option?

[skx]

To be honest I think I'd just remove that restriction; if the user wants to enable it for drafts they can do so via the workflow file - which I guess ties in with your comment in #11.