FloatingMenuSelectWidget: Add 'width' config option
FloatingMenuSelectWidget: Add 'width' config option

Allow the menu to have set width, like popups do.

Change-Id: Ic432dddfc68d2e18d6368a1795d344be79f146bc

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui