78984 [SliverAppBar] Improve dartpad sample in documentation (cla: yes, d: api docs, d: examples, documentation, f: material design, framework, waiting for tree to go green)

f: scrolling - 11 pull request(s)

73526 SliverAppBar Default Elevation Patch (a: quality, cla: yes, f: material design, f: scrolling, framework, waiting for tree to go green)

75095 Fixed improper assertion of maxCrossAxisExtent (cla: yes, f: scrolling, framework)

75761 Added scrollbar example (cla: yes, d: api docs, d: examples, documentation, f: material design, f: scrolling, framework, waiting for tree to go green)

75764 ScrollController.jumpTo zero should not trigger the refresh indicator (cla: yes, f: material design, f: scrolling, framework, waiting for tree to go green)