Update license (#4257)

Co-authored-by: Max Horn <[email protected]>

LICENSE.md

@@ -1,6 +1,11 @@
 The Oscar.jl package is licensed under the GNU Public License, Version 3.0+:
 
-> Copyright (c) 2019 The OSCAR Development Team.
+> Copyright (c) 2019-2024 The OSCAR Development Team
+>
+> See <https://www.oscar-system.org/contributors/> for a list of OSCAR
+> Development Team members. Note that this list may occasionally be slightly
+> outdated. Additional contributors may be found in the `git log` of the main
+> OSCAR repository and other related repositories.
 > This program is free software: you can redistribute it and/or modify
 > it under the terms of the GNU General Public License as published by
 > the Free Software Foundation, either version 3 of the License, or