add missing copyright for 2 header files
I copy/pasted the ones from the cpp.
Note that licencedigger on licencedigger also find missing licences for both CMakeLists.txt. licenseregistry.cpp does not use SPDX statement (UNHANDLED MULTI-LICENSE CASE "licensedigger/licenseregistry.cpp" --> QVector("GPL-2.0-only_OR_GPL-3.0-only_OR_LicenseRef-KDE-Accepted-GPL", "UNKNOWN-LICENSE")).