Add some examples how to query the reports programmatically

This might be a very simple starting point, based on some tests I found:

    /** @var \Drupal\commerce_reports\ReportTypeManager $reportTypeManager */
    $reportTypeManager = \Drupal::service('plugin.manager.commerce_report_type');
    /** @var \Drupal\commerce_reports\ReportQueryBuilder $reportQueryBuilder */
    $reportQueryBuilder = \Drupal::service('commerce_reports.query_builder');
    /** @var \Drupal\commerce_reports\Plugin\Commerce\ReportType\ReportTypeInterface $report_type_plugin */
    $orderReportPlugin = $reportTypeManager->createInstance('order_report');

    $query = $reportQueryBuilder->getQuery($orderReportPlugin);
    $query->accessCheck(TRUE)
      ->range(0, 50)
      ->sort('quantity', 'DESC');

    $results = $query->execute();