[game-data-packager] Optional licenses

[Stephen Kitt <skitt@debian.org>]

Hi,

I've been going through my old CDs, and I've come across a few games which
differ from the variants supported in game-data-packager. Many of these CDs
don't include a license file of any sort, and I'm wondering how to handle
that when the current packaging expects one. For example, in The Dig
(dig.yaml), the-dig-en-data and so on list "end user license agreement.txt"
as a license file; since the CD doesn't include it, g-d-p goes and looks for
it elsewhere, and fails if it can't find it.

How should I go about indicating that the license file is optional?

Regards,

Stephen