Added some Widgets of the Week Videos to documentation (#34758)

* Added some Widgets of the Week to documentation: AspectRatio and AnimatedIcon.

packages/flutter/lib/src/material/animated_icons/animated_icons.dart

@@ -16,6 +16,8 @@ part of material_animated_icons;
 ///
 /// The available icons are specified in [AnimatedIcons].
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=pJcbh8pbvJs}
+///
 /// {@tool sample}
 ///
 /// ```dart

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

@@ -2604,6 +2604,8 @@ class _OffstageElement extends SingleChildRenderObjectElement {
 /// constraints. The height of the widget is determined by applying the
 /// given aspect ratio to the width, expressed as a ratio of width to height.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=XcnP3_mO_Ms}
+///
 /// For example, a 16:9 width:height aspect ratio would have a value of
 /// 16.0/9.0. If the maximum width is infinite, the initial width is determined
 /// by applying the aspect ratio to the maximum height.