Add Awaitable<T>.ToUniTask

src/UniTask/Assets/Plugins/UniTask/Runtime/UnityAwaitableExtensions.cs

@@ -7,6 +7,11 @@ namespace Cysharp.Threading.Tasks
         {
             await awaitable;
         }
+        
+        public static async UniTask<T> AsUniTask<T>(this UnityEngine.Awaitable<T> awaitable)
+        {
+            return await awaitable;
+        }
     }
 }
 #endif