Add a way for GDExtension authors to add their own license text to `Engine.get_copyright_info()` and `Engine.get_license_info()`'s output

[fire]

Describe the project you are working on

V-Sekai is a social VR community.

Describe the problem or limitation you are having in your project

We want to provide accurate licensing as the authors wish.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

Patch onto existing work https://github.com/godotengine/godot/pull/51028 so it can add licenses from gdextension.

Describe how your proposal will work with code, pseudo-code, mock-ups, and/or diagrams

Encode the license text written by the authors into a headless cli and gui section.

Engine.get_copyright_info() and Engine.get_license_info() must return licenses used by the Godot Engine.

A new method like ProjectSettings.get_license_info() may be a way of solving this problem.

Thanks syntaxerror247 for contributing design.

If this enhancement will not be used often, can it be worked around with a few lines of script?

This is a quality of life that makes license compliance easier.

Is there a reason why this should be core and not an add-on in the asset library?

It should be easier for everyone to comply with licenses.

[Calinou]

I'm not sure if this should be part of the output returned by Engine.get_copyright_info() and Engine.get_license_info(), or returned by a different set of methods.

[syntaxerror247]

Engine.get_copyright_info() and Engine.get_license_info() should only return licenses used by the Godot engine. We should definitely create a new method for this, like ProjectSettings.get_license_info().