Force white background behind prevrew iframe regardless of theme to better reflect what the real app will look like

packages/builder/src/components/userInterface/AppPreview/CurrentItemPreview.svelte

@@ -84,6 +84,7 @@
     overflow: hidden;
     margin: auto;
     height: 100%;
+    background-color: white;
   }
   .component-container iframe {
     border: 0;