adds tryPutBeforeUpdating method

LeStorage/StoredSingleton.swift

@@ -27,6 +27,13 @@ public class StoredSingleton<T: SyncedStorable>: SyncedCollection<T> {
         return self.items.first
     }
     
+    public func tryPutBeforeUpdating(_ instance: T) async throws {
+        if let result = try await StoreCenter.main.service().put(instance) {
+            self.setItemNoSync(result)
+        }
+    }
+    
+    
     // MARK: - Protects from use
     
     public override func addOrUpdate(contentOfs sequence: any Sequence<T>) {