added onCompleteAnimation to trigger when animation finished

lib/animation.dart

@@ -15,6 +15,8 @@ class Frame {
   Frame(this.sprite, this.stepTime);
 }
 
+typedef OnCompleteAnimation = void Function();
+
 /// Represents an animation, that is, a list of sprites that change with time.
 class Animation {
   /// The frames that compose this animation.
@@ -34,6 +36,9 @@ class Animation {
   /// Whether the animation loops after the last sprite of the list, going back to the first, or keeps returning the last when done.
   bool loop = true;
 
+  /// Registered method to be triggered when the animation complete.
+  OnCompleteAnimation onCompleteAnimation;
+
   /// Creates an animation given a list of frames.
   Animation(this.frames, {this.loop = true});
 
@@ -204,6 +209,7 @@ class Animation {
       return;
     }
     if (!loop && isLastFrame) {
+      onCompleteAnimation?.call();
       return;
     }
     while (clock > currentFrame.stepTime) {