[wallpapers/image] Add missing PlasmaCore import

wallpapers/image/imagepackage/contents/ui/WallpaperDelegate.qml

@@ -21,6 +21,9 @@ import QtQuick 2.0
 import QtQuick.Controls.Private 1.0
 import QtQuick.Controls 2.3 as QtControls2
 import QtGraphicalEffects 1.0
+
+import org.kde.plasma.core 2.0 as PlasmaCore
+
 import org.kde.kquickcontrolsaddons 2.0
 import org.kde.kirigami 2.4 as Kirigami
 import org.kde.kcm 1.1 as KCM