Support for Java 21 with https://github.com/Goooler/shadow

[tomkeuper]

1 Module of my project has been update to Java 21 but the original ShadowJar library doesnt support java 21. (GradleUp/shadow#876 (comment))

This has been fixed by a fork of the ShadowJar project (https://github.com/Goooler/shadow) but this fork is not supported by slimjar.
Is there a way to add support for this new fork aswell?