Validate game before upload/publish

[jim-toth]

Godot engine has some hooks that you can listen for when game is loaded. On publish screen, could have the game loaded in a preview (also lets creator test it is working) and only allow them to publish if this callback/event from the Godot engine is triggered. Of course, would have to reset this validity state if the uploaded files change.

This might require creating a custom html shell for godot games rather than having the user upload theirs. Alternatively, can temporarily use a custom html shell just for this validity check, but would be nice to investigate if we can somehow listen for this event given any custom html shell from the user

[Nopfed]

Need to replace/add to current game file validation with the ability to check that game loads in browser before publish.