Merge pull request #2013 from leviding/patch-19

Fix minor typo error: add ol number

Author: iliakan

2-ui/1-document/07-modifying-document/article.md

@@ -61,7 +61,7 @@ let div = document.createElement('div');
 // 2. Set its class to "alert"
 div.className = "alert";
 
-// Fill it with the content
+// 3. Fill it with the content
 div.innerHTML = "<strong>Hi there!</strong> You've read an important message.";
 ```