Update cart-builder.html

Author: Shen-wb

barcode-scanner-api-samples/scan-multiple-barcodes/cart-builder.html

@@ -72,8 +72,10 @@
       position: fixed;
       top: 400px;
       left: 100px;
-      width: 400px;
-      height: 200px;
+      width: 50%;
+      height: 25%;
+      max-width: 400px;
+      max-height: 200px;
       background: #f9f9f9;
       border: 2px solid #ccc;
       border-radius: 8px;