[Interest] [Qt6] QML notify dynamic property changes from C++

[Ulf Hermann]

> On a related note, I'd suggest including an iterator/const_iterator for 
> the QQmlPropertyMap for convenience, and also it could possibly handle 
> this sort of value change in a more streamlined manner.

QQmlPropertyMap is not our focus for new features. It's most important 
downside is that we cannot see the properties at compile time. 
Therefore, any QML code that uses it cannot be compiled to C++. However, 
feel free to post changes to https://codereview.qt-project.org and I 
will happily review them.

best regards,
ULf