[Feature Request] Ability to pass ScrollController to PositionedList

[frogman1189]

I would like to be able to use a custom ScrollPosition with the PositionedList. In order to have a scrollController use a custom ScrollPosition you need to extend the scrollController.
As you don't have the ability to provide the scroll controller you must currently fork the package and extend/modify _ListDisplayDetails in order to make this work.