feat: update preview.js with 'overrideParams' for customization

whisk/config/emulsify-core/storybook/preview.js

@@ -1,2 +1,5 @@
-// Import project stylesheets just for Storybook.
-// import '../../../dist/css/style.css';
+// By default, 'overrideParams' is an empty object.
+// Modify this variable to override the default Storybook preview configuration.
+const overrideParams = {};
+
+module.exports = { overrideParams };