Theme Support: use a unique gutenberg key for all the gutenberg the…

…me support features

docs/themes.md

@@ -11,5 +11,7 @@ Some advanced block features require opt-in support in the theme itself as it's
 Some blocks such as the image block have the possibility to define a "wide" or "full" alignment by adding the corresponding classname to the block's wrapper ( `alignwide` or `alignfull` ). A theme can opt-in for this feature by calling:
 
 ```php
-add_theme_support( 'wide-images' );
+add_theme_support( 'gutenberg', array(
+   'wide-images' => true,
+) );
 ```

lib/client-assets.php

@@ -611,8 +611,9 @@ function gutenberg_editor_scripts_and_styles( $hook ) {
 	);
 
 	// Initialize the editor.
+	$gutenberg_theme_support = get_theme_support( 'gutenberg' );
 	$editor_settings = array(
-		'wideImages' => get_theme_support( 'wide-images' ),
+		'wideImages' => $gutenberg_theme_support ? $gutenberg_theme_support[0]['wide-images'] : false,
 	);
 	wp_add_inline_script( 'wp-editor', 'wp.api.init().done( function() {'
 		. 'wp.editor.createEditorInstance( \'editor\', window._wpGutenbergPost, ' . json_encode( $editor_settings ) . ' ); '