FAB Snippet for API Docs (#28752)

* Added code snippets for FloatingActionButton Class. ref:#21136

* Extraneous white spaces.

Co-Authored-By: Piinks <katelovett@google.com>

* Alignment correction.

* The analyze result wasn't showing on github interface. Checked through Cirrus and it's all-green.

Co-Authored-By: Piinks <katelovett@google.com>

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

@@ -53,6 +53,58 @@ class _DefaultHeroTag {
 /// disabled. Consider changing the [backgroundColor] if disabling the floating
 /// action button.
 ///
+/// {@tool snippet --template=stateless_widget_material}
+/// This example shows how to make a simple [FloatingActionButton] in a
+/// [Scaffold], with a pink [backgroundColor] and a thumbs up [Icon].
+///
+/// ```dart
+/// Widget build(BuildContext context) {
+///   return Scaffold(
+///     appBar: AppBar(
+///       title: Text('Floating Action Button Sample'),
+///     ),
+///     body: Center(
+///       child: Text('Press the button below!')
+///     ),
+///     floatingActionButton: FloatingActionButton(
+///       onPressed: () {
+///         // Add your onPressed code here!
+///       },
+///       child: Icon(Icons.thumb_up),
+///       backgroundColor: Colors.pink,
+///     ),
+///   );
+/// }
+/// ```
+/// {@end-tool}
+///
+/// {@tool snippet --template=stateless_widget_material}
+/// This example shows how to make an extended [FloatingActionButton] in a
+/// [Scaffold], with a  pink [backgroundColor] and a thumbs up [Icon] and a
+/// [Text] label.
+///
+/// ```dart
+/// Widget build(BuildContext context) {
+///   return Scaffold(
+///     appBar: AppBar(
+///       title: Text('Floating Action Button Sample'),
+///     ),
+///     body: Center(
+///       child: Text('Press the extended button below!'),
+///     ),
+///     floatingActionButton: FloatingActionButton.extended(
+///       onPressed: () {
+///         // Add your onPressed code here!
+///       },
+///       label: Text('Approve'),
+///       icon: Icon(Icons.thumb_up),
+///       backgroundColor: Colors.pink,
+///     ),
+///   );
+/// }
+/// ```
+/// {@end-tool}
+///
 /// See also:
 ///
 ///  * [Scaffold], in which floating action buttons typically live.