diff -r 34716fd837a4 -r be944660c56a wp/wp-includes/class-wp-theme.php
--- a/wp/wp-includes/class-wp-theme.php	Tue Dec 15 15:52:01 2020 +0100
+++ b/wp/wp-includes/class-wp-theme.php	Wed Sep 21 18:19:35 2022 +0200
@@ -59,6 +59,7 @@
 		'twentyseventeen' => 'Twenty Seventeen',
 		'twentynineteen'  => 'Twenty Nineteen',
 		'twentytwenty'    => 'Twenty Twenty',
+		'twentytwentyone' => 'Twenty Twenty-One',
 	);
 
 	/**
@@ -1140,7 +1141,7 @@
 			return false;
 		}
 
-		foreach ( array( 'png', 'gif', 'jpg', 'jpeg' ) as $ext ) {
+		foreach ( array( 'png', 'gif', 'jpg', 'jpeg', 'webp' ) as $ext ) {
 			if ( file_exists( $this->get_stylesheet_directory() . "/screenshot.$ext" ) ) {
 				$this->cache_add( 'screenshot', 'screenshot.' . $ext );
 				if ( 'relative' === $uri ) {
@@ -1181,6 +1182,7 @@
 	 * Returns the theme's post templates.
 	 *
 	 * @since 4.7.0
+	 * @since 5.8.0 Include block templates.
 	 *
 	 * @return string[] Array of page templates, keyed by filename and post type,
 	 *                  with the value of the translated header name.
@@ -1218,6 +1220,15 @@
 				}
 			}
 
+			if ( current_theme_supports( 'block-templates' ) ) {
+				$block_templates = get_block_templates( array(), 'wp_template' );
+				foreach ( get_post_types( array( 'public' => true ) ) as $type ) {
+					foreach ( $block_templates as $block_template ) {
+						$post_templates[ $type ][ $block_template->slug ] = $block_template->title;
+					}
+				}
+			}
+
 			$this->cache_add( 'post_templates', $post_templates );
 		}
 
@@ -1257,7 +1268,7 @@
 		 * @since 4.9.6
 		 *
 		 * @param string[]     $post_templates Array of template header names keyed by the template file name.
-		 * @param WP_Theme     $this           The theme object.
+		 * @param WP_Theme     $theme          The theme object.
 		 * @param WP_Post|null $post           The post being edited, provided for context, or null.
 		 * @param string       $post_type      Post type to get the templates for.
 		 */
@@ -1268,12 +1279,18 @@
 		 *
 		 * The dynamic portion of the hook name, `$post_type`, refers to the post type.
 		 *
+		 * Possible hook names include:
+		 *
+		 *  - `theme_post_templates`
+		 *  - `theme_page_templates`
+		 *  - `theme_attachment_templates`
+		 *
 		 * @since 3.9.0
 		 * @since 4.4.0 Converted to allow complete control over the `$page_templates` array.
 		 * @since 4.7.0 Added the `$post_type` parameter.
 		 *
 		 * @param string[]     $post_templates Array of template header names keyed by the template file name.
-		 * @param WP_Theme     $this           The theme object.
+		 * @param WP_Theme     $theme          The theme object.
 		 * @param WP_Post|null $post           The post being edited, provided for context, or null.
 		 * @param string       $post_type      Post type to get the templates for.
 		 */