Update preview.ts

Author: DanielCliftonGuardian

dotcom-rendering/.storybook/preview.ts

@@ -163,7 +163,9 @@ export default {
 
 	parameters: {
 		backgrounds: {
+			default: 'transparent',
 			options: {
+				transparent: { name: 'Transparent', value: 'transparent' },
 				grey: { name: 'Grey', value: 'lightgrey' },
 				red: { name: 'Red', value: sourcePalette.news[300] },
 			},
@@ -173,4 +175,11 @@ export default {
 		},
 		layout: 'fullscreen',
 	},
+
+	initialGlobals: {
+		viewport: {
+			value: 'wide',
+			isRotated: false,
+		},
+	},
 } satisfies Preview;