Update licence

Updated years and highlighted that GitHub contributors hold copyright for the code they have contributed.

Update licence
aec7581a · Jeremy Cohen · GitHub · 46bd63f4 · aec7581a
Unverified Commit aec7581a authored 1 year ago by Jeremy Cohen Committed by GitHub 1 year ago
--- a/LICENSE
+++ b/LICENSE
 BSD 3-Clause License

-Copyright (c) 2018, Jeremy Cohen, Imperial College London
+Copyright (c) 2018-2023, Jeremy Cohen, Imperial College London and contributors.
 All rights reserved.

 Redistribution and use in source and binary forms, with or without