Registers the layout block attribute for block types that support it.

function wp_register_layout_support( $block_type ) {
	$support_layout = block_has_support( $block_type, array( '__experimentalLayout' ), false );
	if ( $support_layout ) {
		if ( ! $block_type->attributes ) {
			$block_type->attributes = array();
		}

		if ( ! array_key_exists( 'layout', $block_type->attributes ) ) {
			$block_type->attributes['layout'] = array(
				'type' => 'object',
			);
		}
	}
}