Add CSS resource (#9045)

src/data/roadmaps/full-stack/content/css@dAJHWmGeiYdzZ1ZjrWz1S.md

@@ -7,4 +7,5 @@ Visit the following resources to learn more:
 - [@video@CSS Complete Course](https://youtu.be/n4R2E7O-Ngo)
 - [@video@HTML and CSS Tutorial](https://www.youtube.com/watch?v=D-h8L5hgW-w)
 - [@article@Web.dev by Google — Learn CSS](https://web.dev/learn/css/)
+- [@article@CSS: Cascading Style Sheets | MDN](https://developer.mozilla.org/en-US/docs/Web/CSS)
 - [@feed@Explore top posts about CSS](https://app.daily.dev/tags/css?ref=roadmapsh)