/usr/lib/x86_64-linux-gnu/unity8/qml/Unity/Notifications/qmldir is in qtdeclarative5-unity-notifications-plugin 0.1.3+15.10.20151021-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | module Unity.Notifications
plugin notifyplugin
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