Moving default settings config to a dedicated settings file instead of readme.

Hi,
Thank you for D8 version of this fantastic module. I wanted to make a suggestions for making it easier to integrate this module into a drupal site.

1) I suggest we move "default & suggested settings" config to a dedicated settings file instead of readme. maybe something like example.settings.fast404.php.

2) This file can then be included into the main settings.php file, something like.

/**
 * Load fast404 configuration, if available.
 *
 * Use settings.fast404.php to provide settings for Fast404 module
 *
 * Keep this code block at the end of this file to take full effect.
 */
#
# if (file_exists($app_root . '/' . $site_path . '/settings.fast404.php')) {
#   include $app_root . '/' . $site_path . '/settings.fast404.php';
# }

Any thoughts on this approach?