fix: Support Icons for button dropdown (#3730)

Author: mariksav

pages/button-dropdown/icon-expandable.page.tsx

@@ -6,6 +6,7 @@ import ButtonDropdown, { ButtonDropdownProps } from '~components/button-dropdown
 import SpaceBetween from '~components/space-between';
 
 import AppContext, { AppContextType } from '../app/app-context';
+import img from '../icon/custom-icon.png';
 import ScreenshotArea from '../utils/screenshot-area';
 
 import styles from './styles.scss';
@@ -23,7 +24,8 @@ export const items: ButtonDropdownProps['items'] = [
   {
     id: 'category2',
     text: 'category2',
-    iconUrl: 'data:image/png;base64,aaaa',
+    //New source for iconUrl
+    iconUrl: img,
     items: [...Array(2)].map((_, index) => ({
       id: 'category2Subitem' + index,
       text: 'Cat 2 Sub item ' + index,