Port of KTechLab to Qt6/KF6 ready for more testing

[Zoltan Padrah]

Hi,

in git master I have fixed the crash on document closing.
Based on my testing, also the example menu now shows up correctly.
Some testing of current git master would be useful, to make sure that
everyting works correctly before release.

The windows version of KTechLab currently builds and runs using the
KDE Craft system.

Currently I do not have a timeline for release.
The vesion number of the next release will be most likely 0.60 .

Have fun,

 Zoltan