Update copyright years in README.md

Author: bleykauf

README.md

@@ -63,7 +63,8 @@ License
 
 AISim ‒ Simulations for light-pulse atom interferometry
 
-Copyright © 2023 B. Leykauf, S. Vowe
+Copyright © 2020-2025 B. Leykauf
+Copyright © 2020 S. Vowe
 
 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 (at your option) any later version.