Support the Custom Field module

The module could be updated to add custom_stacked and custom_flex options to the SAM_ALLOWED_WIDGET_TYPES array, but you can actually do this really simply with just one hook implementation.

/**
 * Implements hook_sam_allowed_widget_types_alter().
 */
function MYMODULE_sam_allowed_widget_types_alter(&$widget_types) {
  $widget_types[] = 'custom_stacked';
  $widget_types[] = 'custom_flex';
}