Change color for added menu items and update hover icon

https://core.trac.wordpress.org/ticket/64013

This change makes the added menu item in Customizer WCAG compliant while leaving subtle effects to let the user know that they already added the menu item, but if they want they can add it again.

Author: zerosonesfun

src/wp-admin/css/customize-nav-menus.css

@@ -665,13 +665,17 @@
 #available-menu-items .menu-item-handle.item-added .item-title,
 #available-menu-items .menu-item-handle.item-added:hover .item-add,
 #available-menu-items .menu-item-handle.item-added .item-add:focus {
-	color: #8c8f94;
+	color: #1d2327;
 }
 
 #available-menu-items .menu-item-handle.item-added .item-add:before {
 	content: "\f147" / '';
 }
 
+#available-menu-items .menu-item-handle.item-added:hover .item-add:before {
+	content: "\f543" / '';
+}
+
 #available-menu-items .accordion-section-title.loading .spinner,
 #available-menu-items-search.loading .accordion-section-title .spinner {
 	visibility: visible;