Update copyright in license

Date is not required as documented https://hynek.me/til/copyright-years/
and https://daniel.haxx.se/blog/2023/01/08/copyright-without-years/.

Attribute to all contributors as per https://www.linuxfoundation.org/blog/blog/copyright-notices-in-open-source-software-projects.

LICENSE

@@ -1,6 +1,4 @@
-MIT License
-
-Copyright (c) 2011-2024 Josh Lockhart
+Copyright (c) The Slim-Website contributors
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal