Add a palette editor for Qt Quick Controls 2

One problem that I think might crop up with the palette property of Control (new in Qt 5.10) is knowing which palette role to use for which part of a control. Take button's text colour, for example:

color: control.checked || control.highlighted ? control.palette.brightText :
               control.flat && !control.down ? (control.visualFocus ? control.palette.highlight : control.palette.windowText) : control.palette.buttonText

Having a palette editor (or adding a palette section to the property editor?) would make it easy for users to visually check how a certain palette property affects the visuals of a control.