Add advanced markers sample to readme_sample.dart

Author: aednlaxer

packages/google_maps_flutter/google_maps_flutter/README.md

@@ -125,14 +125,16 @@ in an unbounded widget will cause the application to throw a Flutter exception.
 
 [Advanced Markers](https://developers.google.com/maps/documentation/javascript/advanced-markers/overview) are map markers that offer extra customization options. [Map Id](https://developers.google.com/maps/documentation/get-map-id) is required in order to use Advanced Markers:
 
+
+<?code-excerpt "readme_sample.dart (AdvancedMarkersSample)"?>
 ```dart
 GoogleMap(
   // Set your Map Id
   mapId: 'my-map-id',
   
   // Let map know that you're using Advanced Markers
   markerType: MarkerType.advancedMarker,
-  ...
+  initialCameraPosition: _kGooglePlex,
 ),
 ```
 

packages/google_maps_flutter/google_maps_flutter/example/lib/readme_sample.dart

@@ -8,6 +8,7 @@ import 'dart:async';
 
 import 'package:flutter/material.dart';
 import 'package:google_maps_flutter/google_maps_flutter.dart';
+import 'package:google_maps_flutter_platform_interface/google_maps_flutter_platform_interface.dart';
 
 void main() => runApp(const MyApp());
 
@@ -70,3 +71,28 @@ class MapSampleState extends State<MapSample> {
   }
 }
 // #enddocregion MapSample
+
+// #docregion AdvancedMarkersSample
+class AdvancedMarkersSample extends StatelessWidget {
+  const AdvancedMarkersSample({super.key});
+
+  static const CameraPosition _kGooglePlex = CameraPosition(
+    target: LatLng(37.42796133580664, -122.085749655962),
+    zoom: 14.4746,
+  );
+
+  @override
+  Widget build(BuildContext context) {
+    return const Scaffold(
+      body: GoogleMap(
+        // Set your Map Id
+        mapId: 'my-map-id',
+
+        // Let map know that you're using Advanced Markers
+        markerType: MarkerType.advancedMarker,
+        initialCameraPosition: _kGooglePlex,
+      ),
+    );
+  }
+}
+// #enddocregion AdvancedMarkersSample