A ScrollBehavior that will be applied to this widget individually.
Defaults to null, wherein the inherited ScrollBehavior is copied and modified to alter the viewport decoration, like Scrollbars.
ScrollBehaviors also provide ScrollPhysics. If an explicit ScrollPhysics is provided in scrollPhysics, it will take precedence, followed by scrollBehavior, and then the inherited ancestor ScrollBehavior.
The ScrollBehavior of the inherited ScrollConfiguration will be modified by default to only apply a Scrollbar if maxLines is greater than 1.
final ScrollBehavior? scrollBehavior;