extending-qml example is missing QtQuick dependency in CMakeLists.txt

When trying out qmllint when extending QML with c++, it will fail to recognize the types that have already been exported to qml with QML_ELEMENT.

This can be demonstrated with the 'extending-qml' example, chapter 1. If you run 'ninja all_qmllint' on that it will report this error:

Warning: /Qt/Examples/Qt-6.4.0/qml/tutorials/extending-qml/chapter1-basics/app.qml: QQuickPaintedItem was not found. Did you add all import paths?
Info: Did you mean "PaintedItem"?

Warning: /Qt/Examples/Qt-6.4.0/qml/tutorials/extending-qml/chapter1-basics/app.qml:10:5: 'PieChart' is used but it is not resolved
    PieChart {

The same happens for other base classes such as QQuickItem and QAbstractItemModel to name a few.

Note that this happens even if the piechart sources are moved to the qml module, which they currently are not in the bundled example project.