Twenty Sixteen: Document the twentysixteen_author_avatar_size filter.

Follow-up to [40851].

Props pmbaldha, sabernhardt.
Fixes #63647.

git-svn-id: https://develop.svn.wordpress.org/trunk@61060 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-content/themes/twentysixteen/inc/template-tags.php

@@ -19,6 +19,13 @@
 	 */
 	function twentysixteen_entry_meta() {
 		if ( 'post' === get_post_type() ) {
+			/**
+			 * Filters the Twenty Sixteen entry meta avatar size.
+			 *
+			 * @since Twenty Sixteen 1.0
+			 *
+			 * @param int $size The avatar height and width size in pixels.
+			 */
 			$author_avatar_size = apply_filters( 'twentysixteen_author_avatar_size', 49 );
 			printf(
 				'<span class="byline">%1$s<span class="screen-reader-text">%2$s </span><span class="author vcard"><a class="url fn n" href="%3$s">%4$s</a></span></span>',