fix: retry async test (#52534)

curriculum/challenges/english/15-javascript-algorithms-and-data-structures-22/learn-fetch-and-promises-by-building-an-fcc-authors-page/641da803d9892447d059804e.md

@@ -14,7 +14,19 @@ Now create an image tag and give it the `class` `user-img`. Use template interpo
 You should create an `img` element.
 
 ```js
-assert.exists(document.querySelector('img'));
+const retryingTest = (test, message, tries = 20) => {
+  if (tries < 1) return Promise.reject(message);
+  if (test()) return Promise.resolve();
+
+  return new Promise((resolve, reject) => {
+    setTimeout(() => {
+      retryingTest(test, message, tries - 1)
+        .then(resolve)
+        .catch(reject);
+    }, 100);
+  });
+};
+() => retryingTest(() => document.querySelector('img'), "'img' element not found");
 ```
 
 Your `img` element should have the class `user-img`.