Plasma 6 update

[izissise]

Plasma 6 is out, and krunner now integrate time zone conversion (https://invent.kde.org/plasma/kdeplasma-addons/-/merge_requests/264)

Maybe epochreadable could be merged into the datetime code

[ldriscoll]

that would really be pretty neat. When I have some time, I'll take a look to see how easily it can be done.