WindowManager: Add a $returnFocusTo property
WindowManager: Add a $returnFocusTo property

This gets passed as an argument to openWindow. If defined, the
element gets the focus after the window has been closed.

Bug: T87714
Change-Id: I1199dfb5ef95ce35c0d6175fd70421a8c7407a09

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