config_db.module

<?php

use Drupal\Core\Config\FileStorage;
use Drupal\config_db\Config\DbStorage;

/**
 * Migrate config data from files to db.
 */
function config_db_migrate_config_data() {
  $file_storage = new FileStorage(config_get_config_directory());
  $db_storage = new DbStorage(Drupal::database());
  $config_names = $file_storage->listAll();
  foreach ($file_storage->readMultiple($config_names) as $name => $data) {
    $db_storage->write($name, $data);
  }
}