Unify examples structure (#1118)

* Animations, CameraAndViewport, CollisionDetection and Components unified

* Added descriptions to effects

* Rename input games

* Unify input stories

* Add info to parallax section

* Added descriptions to the rendering examples

* Add descriptions to the sprites directory

* Fix utils and rendering section

* Add descriptions to the widgets section

* Delete directory that rebase brought back

* Unify game names

* Added some styleguide docs for examples

* Fix analyze issues

* All files should have _example as suffix

* Made the FollowComponentExample a bit easier to understand

* Change priority of ember

examples/lib/stories/rendering/layers_example.dart

@@ -0,0 +1,75 @@
+import 'dart:ui';
+
+import 'package:flame/components.dart';
+import 'package:flame/game.dart';
+import 'package:flame/layers.dart';
+
+class LayerExample extends FlameGame {
+  static const String description = '''
+    In this example we show how layers can be used to produce a shadow effect.
+  ''';
+
+  late Layer gameLayer;
+  late Layer backgroundLayer;
+
+  @override
+  Future<void> onLoad() async {
+    await super.onLoad();
+    final playerSprite = Sprite(await images.load('layers/player.png'));
+    final enemySprite = Sprite(await images.load('layers/enemy.png'));
+    final backgroundSprite = Sprite(await images.load('layers/background.png'));
+
+    gameLayer = GameLayer(playerSprite, enemySprite);
+    backgroundLayer = BackgroundLayer(backgroundSprite);
+  }
+
+  @override
+  void render(Canvas canvas) {
+    super.render(canvas);
+    gameLayer.render(canvas);
+    backgroundLayer.render(canvas);
+  }
+
+  @override
+  Color backgroundColor() => const Color(0xFF38607C);
+}
+
+class GameLayer extends DynamicLayer {
+  final Sprite playerSprite;
+  final Sprite enemySprite;
+
+  GameLayer(this.playerSprite, this.enemySprite) {
+    preProcessors.add(ShadowProcessor());
+  }
+
+  @override
+  void drawLayer() {
+    playerSprite.render(
+      canvas,
+      position: Vector2.all(50),
+      size: Vector2.all(150),
+    );
+    enemySprite.render(
+      canvas,
+      position: Vector2(250, 150),
+      size: Vector2(100, 50),
+    );
+  }
+}
+
+class BackgroundLayer extends PreRenderedLayer {
+  final Sprite sprite;
+
+  BackgroundLayer(this.sprite) {
+    preProcessors.add(ShadowProcessor());
+  }
+
+  @override
+  void drawLayer() {
+    sprite.render(
+      canvas,
+      position: Vector2(50, 200),
+      size: Vector2(300, 150),
+    );
+  }
+}