Add a read only property "velocity" to DynamicRigidBody QML type

I'm trying to determine if all objects in a physical simulation are at rest. (or effectively at rest) to allow the user to trigger a new event. It would be much easier if the API had a velocity property I could read for every object and if compare to 0.
See the qt dice demo app for the code needed to achieve this at the moment:
Starting a motion time-out like this:
DynamicRigidBody {
id: root
property real diceWidth: 1.9 // cm
property bool atRest: true
property bool isClose: position.length() < 100
receiveContactReports: true
sendContactReports: true
onBodyContact: (body, positions, impulses, normals) => {
motionTimeout.start()
atRest = false
....

• Timer
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