KQuickStyleItem: Replace manual loop with C++20 std::accumulate
Default operator+ is fine, for QRegion it's the same as the pre-existing united() method.
Unfortunately, there is no std::ranges:: counterpart to avoid the begin-end idiom.
Default operator+ is fine, for QRegion it's the same as the pre-existing united() method.
Unfortunately, there is no std::ranges:: counterpart to avoid the begin-end idiom.