Issue #3283451 by Neslee Canil Pinto: Include hook_install to show welcome message

<?php

/**

 * @file

 * Install, update and uninstall functions for Block Classes.

 */

/**

 * Implements hook_install().

 */

function block_classes_install() {

  \Drupal::messenger()->addStatus(t('Thanks for installing Block Classes. Now in the block configuration you will see a field to add your classes.'));

}