Absolute style path for Virtual Keyboard

There is not any $QT_VIRTUALKEYBOARD_STYLE_PATH today.

The only way of changing the style is by setting its name in $QT_VIRTUALKEYBOARD_STYLE, but then Qt will only look into the Qt Quick 2 plugin directory under ../VirtualKeyboard/Styles/NAME.

I would like to have a similiar syntax as the one for Qt Quick Controls 2 Styles, for which you can change the path where Qt will look:

 - $QT_QUICK_CONTROLS_STYLE_PATH=PATH TO STYLES DIRECTORY , Where Qt looks for styles

 - $QT_QUICK_CONTROLS_STYLE=NAME , Name of the style (checking in the path)