update year in readme

[ci skip]

Author: striezel

readme.md

@@ -125,7 +125,7 @@ A version history is available in [changelog.md](./changelog.md).
 
 ## Copyright and Licensing
 
-Copyright 2018, 2020, 2021, 2022  Dirk Stolle
+Copyright 2018, 2020, 2021, 2022, 2023  Dirk Stolle
 
 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