Update copyright notice

Closes #294

Reviewer Checklist

General code quality

• naming conventions are met (see .clang-tidy for detailed information)
• no static analyzer warnings in new code parts (e.g., use clang-tidy for checking)

General usability

• old versions of pet-files are still loadable

Only if changes in UI

• new elements are also saved and loaded from pet-file
• check if tab order is still correct
• all new SpinBoxes are promoted
• new keybindings added to Petrack::keyBindings()

changed milestone to %1.0.0 - old

added documentation low-effort labels

marked the checklist item naming conventions are met (see .clang-tidy for detailed information) as completed

marked the checklist item no static analyzer warnings in new code parts (e.g., use clang-tidy for checking) as completed

marked the checklist item old versions of pet-files are still loadable as completed

marked the checklist item new elements are also saved and loaded from pet-file as completed

marked the checklist item check if tab order is still correct as completed

marked the checklist item all new SpinBoxes are promoted as completed

marked the checklist item new keybindings added to Petrack::keyBindings() as completed

approved this merge request

added 6 commits

• e3411dd9...61bab137 - 4 commits from branch master
• ae45ea26 - Update copyright notice
• 2bee123f - Remove unintentionally added code lines

Compare with previous version

resolved all threads

enabled an automatic merge when the pipeline for 2bee123f succeeds

merged

mentioned in commit 54fba207