Twenty Seventeen: Document the twentyseventeen_should_show_featured_image filter.

Follow-up to [58206].

Props pmbaldha, kishanjasani, mukesh27, sabernhardt, SergeyBiryukov.
Fixes #63644.

git-svn-id: https://develop.svn.wordpress.org/trunk@60418 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-content/themes/twentyseventeen/functions.php

@@ -708,6 +708,16 @@ function wp_get_list_item_separator() {
  */
 function twentyseventeen_should_show_featured_image() {
 	$show_featured_image = ( is_single() || ( is_page() && ! twentyseventeen_is_frontpage() ) ) && has_post_thumbnail( get_queried_object_id() );
+
+	/**
+	 * Filters whether to show the Twenty Seventeen featured image below the header.
+	 *
+	 * By default, the image is displayed on single posts and pages, unless the page is the front page.
+	 *
+	 * @since Twenty Seventeen 3.7
+	 *
+	 * @param bool $show_featured_image Whether to display the featured image below the header.
+	 */
 	return apply_filters( 'twentyseventeen_should_show_featured_image', $show_featured_image );
 }