Further to Bug-fix Changing Sill _&_ SketchArch Support Sill Property
- https://github.com/FreeCAD/FreeCAD/pull/21726 ,
minor fix to make ensure tracking of sill works upon window creation.
User has no possibility to change Sill parameter upon adding Window, it
is only possible while creating Window for the first time.
So this patch adds this parameter, and changing it moves the *BASE*
coordinate of the object in Z direction.
