feat(napi): implement with_optional_signal on AsyncTask

crates/napi/src/bindgen_runtime/js_values/task.rs

@@ -35,6 +35,13 @@ impl<T: Task> AsyncTask<T> {
       abort_signal: Some(signal),
     }
   }
+
+  pub fn with_optional_signal(task: T, signal: Option<AbortSignal>) -> Self {
+    Self {
+      inner: task,
+      abort_signal: signal,
+    }
+  }
 }
 
 /// https://developer.mozilla.org/zh-CN/docs/Web/API/AbortController