Added a new resource (OWASP#969)

Hey, I have added a reference link for HTML Links under Tabnabbing. I came upon this article while looking for resources to learn HTML. This citation, in my opinion, will enhance the content of this article. Hope that my contribution will benefit other learners.

cheatsheets/HTML5_Security_Cheat_Sheet.md

@@ -97,7 +97,7 @@ Cut the back link between the parent and the child pages:
 
 As the behavior using the elements above is different between the browsers, either use an HTML link or JavaScript to open a window (or tab), then use this configuration to maximize the cross supports:
 
-- For HTML links, add the attribute `rel="noopener noreferrer"` to every link.
+- For [HTML links](https://www.scaler.com/topics/html/html-links/), add the attribute `rel="noopener noreferrer"` to every link.
 - For JavaScript, use this function to open a window (or tab):
 
 ``` javascript