Merge pull request #16 from VGVentures/doc/wall-docs

docs: adding dart docs to the wall component

lib/game/components/wall.dart

@@ -3,6 +3,9 @@
 import 'package:flame_forge2d/flame_forge2d.dart';
 import 'package:pinball/game/components/components.dart';
 
+/// {@template wall}
+/// A continuos generic and [BodyType.static] barrier that divides a game area.
+/// {@endtemplate}
 class Wall extends BodyComponent {
   Wall({
     required this.start,
@@ -29,6 +32,12 @@ class Wall extends BodyComponent {
   }
 }
 
+/// {@template bottom_wall}
+/// [Wall] located at the bottom of the board.
+///
+/// Collisions with [BottomWall] are listened by
+/// [BottomWallBallContactCallback].
+/// {@endtemplate}
 class BottomWall extends Wall {
   BottomWall(Forge2DGame game)
       : super(
@@ -40,6 +49,9 @@ class BottomWall extends Wall {
         );
 }
 
+/// {@template bottom_wall_ball_contact_callback}
+/// Listens when a [Ball] falls into a [BottomWall].
+/// {@endtemplate}
 class BottomWallBallContactCallback extends ContactCallback<Ball, BottomWall> {
   @override
   void begin(Ball ball, BottomWall wall, Contact contact) {