Add close button to introduction banner card.

plugins/woocommerce-admin/client/marketing/overview-multichannel/IntroductionBanner/IntroductionBanner.scss

@@ -34,6 +34,13 @@
 			rgba( 196, 152, 217, 0.12 ) 77.75%
 		);
 
+		.woocommerce-marketing-introduction-banner-close-button {
+			position: absolute;
+			top: $gap-smaller;
+			right: $gap;
+			padding: 0;
+		}
+
 		img {
 			display: block;
 			width: 100%;

plugins/woocommerce-admin/client/marketing/overview-multichannel/IntroductionBanner/IntroductionBanner.tsx

@@ -2,8 +2,14 @@
  * External dependencies
  */
 import { __ } from '@wordpress/i18n';
-import { Card, Flex, FlexItem, FlexBlock } from '@wordpress/components';
+import { Card, Flex, FlexItem, FlexBlock, Button } from '@wordpress/components';
-import { Icon, trendingUp, megaphone } from '@wordpress/icons';
+import {
+	Icon,
+	trendingUp,
+	megaphone,
+	closeSmall,
+	close,
+} from '@wordpress/icons';
 
 /**
  * Internal dependencies
@@ -73,6 +79,15 @@ export const IntroductionBanner = () => {
 				</Flex>
 			</div>
 			<div className="woocommerce-marketing-introduction-banner-illustration">
+				<Button
+					isSmall
+					className="woocommerce-marketing-introduction-banner-close-button"
+					onClick={ () => {
+						// TODO: dismiss this banner and save it into wp_options.
+					} }
+				>
+					<Icon icon={ closeSmall } />
+				</Button>
 				<img
 					src={ illustrationUrl }
 					alt={ __(