Add ThreadPoolScheduler

Scripts/UniTask/ThreadPoolScheduler.cs

@@ -0,0 +1,42 @@
+using System;
+
+namespace UniTask
+{
+    public static partial class Scheduler
+    {
+        private static IScheduler threadPool;
+
+        public static IScheduler ThreadPool
+        {
+            get { return threadPool ?? (threadPool = new ThreadPoolScheduler()); }
+        }
+
+        public class ThreadPoolScheduler : IScheduler
+        {
+            public void Enqueue(TaskChain item)
+            {
+                System.Threading.ThreadPool.QueueUserWorkItem(_ =>
+                {
+                    if (item == null)
+                    {
+                        return;
+                    }
+
+                    while (true)
+                    {
+                        var status = item.Next();
+                        if (status != ExecutionStatus.Continue)
+                        {
+                            break;
+                        }
+                    }
+
+                });
+            }
+
+            public void Dispose()
+            {
+            }
+        }
+    }
+}