Add license to attribute project members

[and-rad]

The license should be used to attribute not third-party assets, but people who work directly on the project, either as an employee or a contractor. The point of the license is to provide a way to fill the Credits section of the credits resource automatically. To that end, the license will have a Role property that is used to find the correct role in the resource.

On Godot 4.2, this requires a new property in the credits resource to store these attributions separately from the third-party attributions. The attribution manager needs to detect them and sort them in the right bucket.

[and-rad]

When godotengine/godot#72912 makes it into a stable release, this can be solved a little more elegantly.