Add new widget of the week videos (#107301)

Author: guidezpl

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

@@ -15,10 +15,12 @@ import 'navigation_rail_theme.dart';
 import 'text_theme.dart';
 import 'theme.dart';
 
-/// A material widget that is meant to be displayed at the left or right of an
+/// A Material Design widget that is meant to be displayed at the left or right of an
 /// app to navigate between a small number of views, typically between three and
 /// five.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=y9xchtVTtqQ}
+///
 /// The navigation rail is meant for layouts with wide viewports, such as a
 /// desktop web or tablet landscape layout. For smaller layouts, like mobile
 /// portrait, a [BottomNavigationBar] should be used instead.

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

@@ -1030,6 +1030,8 @@ class _ActionsMarker extends InheritedWidget {
 /// and key bindings, and provides callbacks for handling focus and hover
 /// highlights.
 ///
+/// {@youtube 560 315 https://www.youtube.com/watch?v=R84AGg0lKs8}
+///
 /// This widget can be used to give a control the required detection modes for
 /// focus and hover handling. It is most often used when authoring a new control
 /// widget, and the new control should be enabled for keyboard traversal and