69781 Added dartpad examples for SliverAppBar (adopt a widget, cla: yes, d: api docs, d: examples, documentation, f: material design, framework, team, waiting for tree to go green)

70184 [FloatingActionButtonLocation] Add diagrams to documentation of FloatingActionButtonLocation (cla: yes, d: api docs, d: examples, documentation, f: material design, framework, waiting for tree to go green)

70343 Code sample small fixes (adopt a widget, cla: yes, d: api docs, f: material design, framework, waiting for tree to go green)

70379 Added Tabar Code samples (adopt a widget, cla: yes, d: api docs, d: examples, documentation, f: material design, framework, waiting for tree to go green)