feat: add EnsureBundleFileAsync operation

Assets/YooAsset/Runtime/ResourcePackage/BundleInfo.cs

@@ -50,6 +50,16 @@ namespace YooAsset
             return _fileSystem.LoadPackageBundleAsync(options);
         }
 
+        /// <summary>
+        /// 创建资源包文件确保器
+        /// </summary>
+        /// <returns>返回确保资源包文件就绪的操作对象</returns>
+        public FSEnsurePackageBundleOperation CreateBundleEnsurer()
+        {
+            var options = new FSEnsurePackageBundleOptions(Bundle);
+            return _fileSystem.EnsurePackageBundleAsync(options);
+        }
+
         /// <summary>
         /// 创建资源包下载器
         /// </summary>