Customize: Trailingslash the home nav menu item URL in starter content.

This prevents an additional 301 redirect when clicking on the nav menu item, and it also prevents a scenario where the auth cookie may not be passed and cause an authentication error when navigating in the customizer.

Props dlh, swissspidy.
Fixes #40112.

Built from https://develop.svn.wordpress.org/trunk@40300


git-svn-id: http://core.svn.wordpress.org/trunk@40207 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/theme.php

@@ -1984,7 +1984,7 @@ function get_theme_starter_content() {
 			'link_home' => array(
 				'type' => 'custom',
 				'title' => _x( 'Home', 'Theme starter content' ),
-				'url' => home_url(),
+				'url' => home_url( '/' ),
 			),
 			'page_home' => array( // Deprecated in favor of link_home.
 				'type' => 'post_type',