Document all available properties in Qt Quick Universal Style, including the readonly ones

The docs for the Universal style only include 4 properties: https://doc.qt.io/qt-6/qtquickcontrols-universal.html

Namely accent, background, foreground and theme.

But in reality a lot more properties are available. One need just look at the source code for TextField: https://github.com/qt/qtdeclarative/blob/dev/src/quickcontrols/universal/TextField.qml

These properties under Universal such as chromeWhiteColor, chromeDisabledLowColor, chromeBlackMediumLowColor, baseMediumColor are all entirely available when writing QML code. In fact we are already using them to make custom components compatible with the Universal style. It makes sense to document them as such.

Seems like they are all defined in https://github.com/qt/qtdeclarative/blob/bc5e56bcce2618b7810cf2f4007bf4370dc3bbc9/src/quickcontrols/universal/qquickuniversalstyle.cpp