add string AJAX to fetch example

Author: jcubic

docs/docs/lips/intro.md

@@ -696,7 +696,7 @@ next expression.
 ```
 
 This simplifies code when using promises, for instance using
-[fetch API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API).
+[fetch API](https://developer.mozilla.org/en-US/docs/Web/API/Fetch_API) (AJAX).
 
 ```scheme
 (--> (fetch "https://scheme.org.pl/test/") (text) (match #/<h1>([^>]+)<\/h1>/) 1)