Add Dependencies to steamworks.Publish

[Denneisk]

Exposing adding UGC dependencies when uploading dupes/saves will make things simpler for dupe/save users and creators.

Gmod has the functionality to detect dependencies, which is good, but you can't tell what these dependencies are before you load the dupe, and you can't browse the dependencies at all in a save.

Ideally, additionally, a menu would let the creator pick and choose which dependencies are included by extending the UGCPublishWindow panel.