Godot Export config changes required to get MacOS builds working

[kmturley]

Here is a list of Godot Export config changes I had to make to get MacOS builds working:
(In addition to: #145)

1. Export path should end with .app

2. Codesign option should be set to Built-in (ad-hoc only)

3. Notorization should be set to Disabled

Could the README be updated to document these? This would save others time.