sliver library Null safety

Class for creating Sliver widgets. The Flutter SDK uses the Widget class but can lead to improper usage.

https://docs.flutter.dev/development/ui/advanced/slivers

This contains Slivers that are part of the Flutter SDK.

Classes

Sliver
SliverAppBar
SliverAppBarLarge
SliverAppBarMedium
SliverFillRemaining
SliverFillViewport
SliverFixedExtentList
SliverGrid
SliverIgnorePointer
SliverList
SliverOffstage
SliverOpacity
SliverPadding
SliverPrototypeExtentList
SliverSafeArea
SliverToBoxAdapter
SliverVisibility
SliverVisibilityMaintain