docs: update license year (#7314)

stefan-kolb · web-flow · commit facc800dbbe3 · 2021-01-08T12:37:30.000+01:00
diff --git a/LICENSE.md b/LICENSE.md
@@ -1,6 +1,6 @@
 MIT License
 
-Copyright © 2003-2020 [JabRef Authors](https://github.com/JabRef/jabref/blob/master/AUTHORS)
+Copyright © 2003-2021 [JabRef Authors](https://github.com/JabRef/jabref/blob/master/AUTHORS)
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
