add or append to existing metadata changelog file if fixing inconsistencies

add like:

2025-06-06  Ubbo Veentjer  <veentjer@sub.uni-goettingen.de>
        
        add lang field to edition, see https://gitlab.gwdg.de/dariah-de/textgridrep/repository-maintenance/2025-06-05-add-lang-to-digibib/