This also moves Widget::load_from_json into Core::Object as a virtual
function in order to allow loading non-widget objects in GML (e.g.
BoxLayout).
Co-authored-by: Gunnar Beutner <gbeutner@serenityos.org>
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
