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

Source/MonoGame.Extended.Particles/Modifiers/RotationModifier.cs

@@ -0,0 +1,18 @@
+namespace MonoGame.Extended.Particles.Modifiers
+{
+    public class RotationModifier : IModifier
+    {
+        public float RotationRate { get; set; }
+
+        public unsafe void Update(float elapsedSeconds, ParticleBuffer.ParticleIterator iterator)
+        {
+            var rotationRateDelta = RotationRate*elapsedSeconds;
+
+            while (iterator.HasNext)
+            {
+                var particle = iterator.Next();
+                particle->Rotation += rotationRateDelta;
+            }
+        }
+    }
+}