photosurface example: CMake warning QTP0004

CMake Warning (dev) at /Users/kkoehne/Qt/6.10.0/macos/lib/cmake/Qt6Core/Qt6CoreMacros.cmake:3407 (message):
  Qt policy QTP0004 is not set: You need qmldir files for each extra
  directory that contains .qml files for your module.  Check
  https://doc.qt.io/qt-6/qt-cmake-policy-qtp0004.html for policy details.
  Use the qt_policy command to set the policy and suppress this warning.

Call Stack (most recent call first):
  /Users/kkoehne/Qt/6.10.0/macos/lib/cmake/Qt6Qml/Qt6QmlMacros.cmake:3773 (__qt_internal_setup_policy)
  /Users/kkoehne/Qt/6.10.0/macos/lib/cmake/Qt6Qml/Qt6QmlMacros.cmake:925 (qt6_target_qml_sources)
  content/CMakeLists.txt:6 (qt6_add_qml_module)
This warning is for project developers.  Use -Wno-dev to suppress it.