Add more breadcrumb docs to Transformation (#31420)

packages/flutter/lib/src/widgets/basic.dart

@@ -991,6 +991,11 @@ class PhysicalShape extends SingleChildRenderObjectWidget {
 
 /// A widget that applies a transformation before painting its child.
 ///
+/// Unlike [RotatedBox], which applies a rotation prior to layout, this object
+/// applies its transformation just prior to painting, which means the
+/// transformation is not taken into account when calculating how much space
+/// this widget's child (and thus this widget) consumes.
+///
 /// {@youtube 560 315 https://www.youtube.com/watch?v=9z_YNlRlWfA}
 ///
 /// {@tool sample}