moved the particle system and the entity component system into their own nuget packages

Source/MonoGame.Extended.Entities/Systems/AnimatedSpriteSystem.cs

@@ -0,0 +1,19 @@
+using System.Linq;
+using Microsoft.Xna.Framework;
+using MonoGame.Extended.Entities.Components;
+using MonoGame.Extended.Sprites;
+
+namespace MonoGame.Extended.Entities.Systems
+{
+    public class AnimatedSpriteSystem : ComponentSystem
+    {
+        public override void Update(GameTime gameTime)
+        {
+            var deltaTime = gameTime.GetElapsedSeconds();
+            var sprites = GetComponents<TransformableComponent<Sprite>>();
+
+            foreach (var animatedSprite in sprites.Select(c => c.Target).OfType<AnimatedSprite>())
+                animatedSprite.Update(deltaTime);
+        }
+    }
+}