[plasmoidviewer] Pick up KQuickAddons::QtQuickSettings
Summary:
If having the need to use those settings with something else than the
default, one also expects the utils to follow those custom settings.
Reviewers: Plasma, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D18626