上传框架，上传unitask

Assets/08.UniTask/Runtime/Linq/Empty.cs

@@ -0,0 +1,47 @@
+using System.Threading;
+
+namespace Cysharp.Threading.Tasks.Linq
+{
+    public static partial class UniTaskAsyncEnumerable
+    {
+        public static IUniTaskAsyncEnumerable<T> Empty<T>()
+        {
+            return Cysharp.Threading.Tasks.Linq.Empty<T>.Instance;
+        }
+    }
+
+    internal class Empty<T> : IUniTaskAsyncEnumerable<T>
+    {
+        public static readonly IUniTaskAsyncEnumerable<T> Instance = new Empty<T>();
+
+        Empty()
+        {
+        }
+
+        public IUniTaskAsyncEnumerator<T> GetAsyncEnumerator(CancellationToken cancellationToken = default)
+        {
+            return _Empty.Instance;
+        }
+
+        class _Empty : IUniTaskAsyncEnumerator<T>
+        {
+            public static readonly IUniTaskAsyncEnumerator<T> Instance = new _Empty();
+
+            _Empty()
+            {
+            }
+
+            public T Current => default;
+
+            public UniTask<bool> MoveNextAsync()
+            {
+                return CompletedTasks.False;
+            }
+
+            public UniTask DisposeAsync()
+            {
+                return default;
+            }
+        }
+    }
+}