Update first-visit modal: clarify desktop recommendation and demo-only notice

src/scripts/demo-modal.js

@@ -27,7 +27,7 @@ document.addEventListener("DOMContentLoaded", () => {
 
         let message = document.createElement("p");
         message.innerText =
-            "This site is for demonstration purposes only and is not a real e-commerce store. No purchases can be made.";
+            "This site is best viewed using a desktop browser. It is for demonstration purposes only and is not a real e-commerce store. No purchases can be made.";
 
         let closeButton = document.createElement("button");
         closeButton.innerText = "I Understand";