Update Rectangle gradient code example

Currently in the Rectangle gradient property section, the code example for creating a horizontal gradient uses the rotation property and not the Gradient orientation property. This could be misleading to the user as it gives the impression that the rectangle needs to be rotated in order to create a horizontal gradient. 

https://doc.qt.io/qt-6/qml-qtquick-rectangle.html#gradient-prop

The suggestion is to update the horizontal gradient example or add another example which demonstrates the use of the Gradient orientation property to create a horizontal gradient.

Rectangle {
    y: 200; width: 80; height: 80
    gradient: Gradient {
        orientation: Gradient.Horizontal
        GradientStop { position: 0.0; color: "lightsteelblue" }
        GradientStop { position: 1.0; color: "blue" }
    }
}