66834 GlobalKey docs improvement (cla: yes, d: api docs, documentation, framework)

66972 Nested Scaffolds - Suggested Changes (cla: yes, d: api docs, f: material design, framework)

67066 docs for image disposal (cla: yes, d: api docs, framework)

67585 Add documentation talking about ScrollPhysics.applyTo(null) (cla: yes, d: api docs, documentation, framework, waiting for tree to go green)

67811 Fix typos in the [BottomNavigationBar] document (cla: yes, d: api docs, f: material design, framework, waiting for tree to go green)

67940 Fix NestedScrollView sample code (a: quality, cla: yes, d: api docs, d: examples, documentation, framework, waiting for tree to go green)