Copy the aurorae decoration qml plugin to bin dir in build directory

Summary:
Look there, another plugin I didn't remember. The other qml files are
not needed for the aurorae autotest as it's for the svg based themes
instead of qml themes like Plastik.

Test Plan: Further destroyed my system, test failed, with this change passed.

Reviewers: #kwin

Subscribers: kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D16761