Allows to set the application's license froma list of known licenses.
If the application's license is not in the list, property@AboutWindow:license can be used instead. The license type will be automatically set to [gtk.types.License.Custom] in that case.
If set to [gtk.types.License.Unknown], no information will be displayed.
If the license type is different from [gtk.types.License.Custom]. property@AboutWindow:license will be cleared out.
The license description will be displayed on the Legal page, below the copyright information.
[adw.about_window.AboutWindow.addLegalSection] can be used to add license information for the application dependencies or other components.