feat: clampLength for Vector2 extension (#2190)

With this method you can clamp the length of a vector, instead fitting it in a box like clamp and clampScalar does.

examples/lib/stories/rendering/isometric_tile_map_example.dart

@@ -32,6 +32,7 @@ class IsometricTileMapExample extends FlameGame with MouseMovementDetector {
 
   @override
   Future<void> onLoad() async {
+    debugMode = true;
     final tilesetImage = await images.load('tile_maps/tiles$suffix.png');
     final tileset = SpriteSheet(
       image: tilesetImage,