Add screencast to NFT tutorial (#503)

src/pages/developers/tutorials/nft.mdx

@@ -3,6 +3,18 @@ import { Alert } from "~/components/shared";
 In this tutorial you will learn how to create a universal ERC-721 NFT that can
 be easily transferred between chains connected to ZetaChain.
 
+<div className="mt-8" style={{ width: "100%", height: "auto", "aspect-ratio": "16 / 8" }}>
+  <iframe
+    width="100%"
+    height="100%"
+    src="https://www.youtube.com/embed/fRv1iyi1IjQ?si=R02nUzS0NpoclZa_"
+    filename="YouTube video player"
+    frameborder="0"
+    allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"
+    allowfullscreen
+  ></iframe>
+</div>
+
 The project consists of two ERC-721 NFT contracts.
 
 **Universal** contract is deployed on ZetaChain. The contract is used to: