Frameworks master is Qt6 now

[Nicolas Fella]

Hi,

the master branch of frameworks repositories now required Qt6 to build.
Maintenance of KF5 continues in the "kf5" branch.

Those using kdesrc-build make sure your kdesrc-builrc contains
"branch-group kf5-qt5", then it will switch to the correct branch
automatically.

Those building manually please adjust your workflow accordingly.

Any merge requests for frameworks should target Qt6/master (unless they
are not applicable there). If the change should be backported to KF5
cherry-pick it to the kf5 branch after merging.

Note that for the time being the kf5 branch has to stay compatible with
Qt6. This is required to keep the currently existing Qt6 builds working.

This does *not* mean that master is now open for any kind of breaking
change. We will announce more on this soon.

Cheers

Nicolas