Toggle buttons docs (#38635)

* Add toggle buttons assets

* Reorder video location, reduce height of videos

* Reduce height of toggle buttons assets

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

@@ -26,6 +26,8 @@ import 'toggle_buttons_theme.dart';
 /// Each toggle's behavior can be configured by the [onPressed] callback, which
 /// can update the [isSelected] list however it wants to.
 ///
+/// {@animation 700 150 https://flutter.github.io/assets-for-api-docs/assets/material/toggle_buttons_simple.mp4}
+///
 /// Here is an implementation that allows for multiple buttons to be
 /// simultaneously selected, while requiring none of the buttons to be
 /// selected.
@@ -45,6 +47,8 @@ import 'toggle_buttons_theme.dart';
 /// ),
 /// ```
 ///
+/// {@animation 700 150 https://flutter.github.io/assets-for-api-docs/assets/material/toggle_buttons_required_mutually_exclusive.mp4}
+///
 /// Here is an implementation that requires mutually exclusive selection
 /// while requiring at least one selection. Note that this assumes that
 /// [isSelected] was properly initialized with one selection.
@@ -70,6 +74,8 @@ import 'toggle_buttons_theme.dart';
 /// ),
 /// ```
 ///
+/// {@animation 700 150 https://flutter.github.io/assets-for-api-docs/assets/material/toggle_buttons_mutually_exclusive.mp4}
+///
 /// Here is an implementation that requires mutually exclusive selection,
 /// but allows for none of the buttons to be selected.
 /// ```dart
@@ -94,6 +100,8 @@ import 'toggle_buttons_theme.dart';
 /// ),
 /// ```
 ///
+/// {@animation 700 150 https://flutter.github.io/assets-for-api-docs/assets/material/toggle_buttons_required.mp4}
+///
 /// Here is an implementation that allows for multiple buttons to be
 /// simultaneously selected, while requiring at least one selection. Note
 /// that this assumes that [isSelected] was properly initialized with one