Add an explicit instantiation declaration to suppress compiler warning.
The warning is
/home/arr/projects/kderoot/download/git/kde/frameworks/tier1/kirigami/src/libkirigami/basictheme.cpp:277:65: warning: instantiation of variable 'Kirigami::PlatformThemeEvents::PropertyChangedEvent<std::shared_ptr<Kirigami::PlatformThemeData>>::type' required here, but no definition is available [-Wundefined-var-template]
if (event->type() == PlatformThemeEvents::DataChangedEvent::type) {
^
/home/arr/projects/kderoot/download/git/kde/frameworks/tier1/kirigami/src/libkirigami/platformtheme.h:370:25: note: forward declaration of template entity is here
static QEvent::Type type;
^
/home/arr/projects/kderoot/download/git/kde/frameworks/tier1/kirigami/src/libkirigami/basictheme.cpp:277:65: note: add an explicit instantiation declaration to suppress this warning if 'Kirigami::PlatformThemeEvents::PropertyChangedEvent<std::shared_ptr<Kirigami::PlatformThemeData>>::type' is explicitly instantiated in another translation unit
if (event->type() == PlatformThemeEvents::DataChangedEvent::type) {
^