Reuse Chapter 2 responsive iframe styles in Chapter 3 introduction (#475)

* chore(ui): update iframe styles for responsive video embed

* added closing tag of div

Author: naman79820

docs/chapter3/1introduction.md

@@ -10,12 +10,11 @@ The CircuitVerse simulator includes different sections for building and managing
 
 <div>
   <iframe
-    width="1424"
-    height="592"
     src="https://www.youtube.com/embed/F-_uvYJK938"
+    style="width: 100%; aspect-ratio: 16 / 9;"
     title="YouTube video player"
     frameborder="0"
     allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"
     allowfullscreen
   ></iframe>
-</div>
+</div>