fix(docs): add link to article for interlude 4

Author: MinaPecheux

README.md

@@ -114,6 +114,8 @@ You can find the list of all tutorials [on Medium](https://medium.com/c-sharp-pr
 
 <li>Tutorial #49: <a href="https://mina-pecheux.medium.com/making-a-rts-game-49-optimisation-tips-tricks-unity-c-d4d70001e58c" rel="noopener follow"><strong>Optimisation tips & tricks</strong></a></li>
 
+<li>Interlude #4: <a href="https://mina-pecheux.medium.com/rts-interlude-4-improving-the-healthbars-unity-c-48ee8d663e09" rel="noopener follow"><strong>Improving the healthbars</strong></a></li>
+
 </ul>
 
 ## Known issues