designtopack/public/site/plugins/notifications/index.php

<?php

Kirby::plugin('adrienpayet/pdc-notifications', [
  'routes' => [
    require(__DIR__ . '/routes/mark-as-read.php'),
  ],
  'userMethods' => [
    'sendNotification' => require(__DIR__ . '/user-methods/send.php')
  ]
]);