feat: Adding ImageExtension.resize (#2418)

Adds a helper method to ImageExtension to make it easier to resize an image.

examples/lib/stories/image/image.dart

@@ -0,0 +1,23 @@
+import 'package:dashbook/dashbook.dart';
+
+import 'package:examples/commons/commons.dart';
+import 'package:examples/stories/image/resize.dart';
+import 'package:flame/game.dart';
+
+void addImageStories(Dashbook dashbook) {
+  dashbook.storiesOf('Image')
+    ..decorator(CenterDecorator())
+    ..add(
+      'resize',
+      (context) => GameWidget(
+        game: ImageResizeExample(
+          Vector2(
+            context.numberProperty('width', 200),
+            context.numberProperty('height', 300),
+          ),
+        ),
+      ),
+      codeLink: baseLink('image/resize.dart'),
+      info: ImageResizeExample.description,
+    );
+}

examples/lib/stories/image/resize.dart

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+import 'package:flame/components.dart';
+import 'package:flame/extensions.dart';
+import 'package:flame/game.dart';
+
+class ImageResizeExample extends FlameGame {
+  ImageResizeExample(this.sizeTarget);
+
+  static const String description = '''
+     Shows how a dart:ui `Image` can be resized using Flame Image extensions.
+     Use the properties on the side to change the size of the image.
+  ''';
+
+  final Vector2 sizeTarget;
+
+  @override
+  Future<void> onLoad() async {
+    final image = await images.load('flame.png');
+
+    final resized = await image.resize(sizeTarget);
+    add(
+      SpriteComponent(
+        sprite: Sprite(resized),
+        position: size / 2,
+        size: resized.size,
+        anchor: Anchor.center,
+      ),
+    );
+  }
+}