Add widget of the week videos (#32982)

* AnimatedList
* Flexible
* Draggable
* ValueListenableBuilder

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

@@ -44,6 +44,8 @@ class _ActiveItem implements Comparable<_ActiveItem> {
 /// use the static [of] method from an item's input callback.
 ///
 /// This widget is similar to one created by [ListView.builder].
+///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=ZtfItHwFlZ8}
 class AnimatedList extends StatefulWidget {
   /// Creates a scrolling container that animates items when they are inserted or removed.
   const AnimatedList({

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

@@ -4253,6 +4253,8 @@ class Column extends Flex {
 /// [Flex] must contain only [StatelessWidget]s or [StatefulWidget]s (not other
 /// kinds of widgets, like [RenderObjectWidget]s).
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=CI7x0mAZiY0}
+///
 /// See also:
 ///
 ///  * [Expanded], which forces the child to expand to fill the available space.

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

@@ -87,6 +87,8 @@ enum DragAnchor {
 /// [childWhenDragging] when one or more drags are underway. Otherwise, this
 /// widget always displays [child].
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=QzA4c4QHZCY}
+///
 /// See also:
 ///
 ///  * [DragTarget]

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

@@ -25,6 +25,8 @@ typedef ValueWidgetBuilder<T> = Widget Function(BuildContext context, T value, W
 /// listener of the [ValueListenable] and call the [builder] with updated values
 /// when the value changes.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=s-ZG-jS5QHQ}
+///
 /// ## Performance optimizations
 ///
 /// If your [builder] function contains a subtree that does not depend on the