Update html@yWG2VUkaF5IJVVut6AiSy.md --added free course-cert link to HTML & CSS

Added "freeCodeCamp | Responsive Web Design Certification" to HTML and CSS. [url: "

https://www.freecodecamp.org/learn/2022/responsive-web-design/

"]
It is a free certification with step-by-step guided projects in HTML & CSS.
The final project is even your first webpage portfolio.

src/data/roadmaps/frontend/content/html@yWG2VUkaF5IJVVut6AiSy.md

@@ -8,3 +8,4 @@ Visit the following resources to learn more:
 - [@video@HTML Full Course for Beginners](https://youtu.be/mJgBOIoGihA)
 - [@video@HTML Full Course - Build a Website Tutorial](https://www.youtube.com/watch?v=pQN-pnXPaVg)
 - [@feed@Explore top posts about HTML](https://app.daily.dev/tags/html?ref=roadmapsh)
+- [@course@Responsive Web Design Certification - Co-Learn HTML & CSS with guided projects](https://www.freecodecamp.org/learn/2022/responsive-web-design/)