Add support for 6.7 runtime

[imoBooze]

I did some testing and it seems to build and work fine. Looking at the previous MRs, it should be merged into branch/6.7. This would close #29 .

[flathubbot]

Started test build 119707

[flathubbot]

Build 119707 successful
To test this build, install it from the testing repository:

flatpak install --user https://dl.flathub.org/build-repo/102555/org.kde.KStyle.Kvantum.flatpakref

[Play-InTheWay]

What does remain to do, or how long will it take to merge?

[LSeelig]

@imoBooze I cannot install your test build because it has expired. How can I regenerate it?

[Play-InTheWay]

@imoBooze I cannot install your test build because it has expired. How can I regenerate it?

@LSeelig If you want to test it for yourself, you can download org.kde.KStyle.Kvantum.json and org.kde.KStyle.Kvantum.appdata from the branch of ImoBooze

Then use
flatpak-builder --force-clean --user --install-deps-from=flathub --repo=repo --install builddir org.kde.KStyle.Kvantum.json
(both files have to be in the same place)
Though, it's the first time that I build a flatpak, but for me that worked just fine.