Add drush/drush as a dependency

[nikathone]

Was testing this with drupalvm and got TASK [geerlingguy.drupal : Install Drupal with drush.] ************************* fatal: [commercevm]: FAILED! => {"changed": true, "cmd": ["drush", "site-install", "commerce_base", "-y", "--root=/var/www/drupalvm/drupal/web", "--site-name=Drupal", "--account-name=admin", "--account-pass=admin", "--db-url=mysql://drupal:drupal@localhost/drupal"], "delta": "0:00:00.025883", "end": "2018-04-23 20:30:21.964442", "msg": "non-zero return code", "rc": 1, "start": "2018-04-23 20:30:21.938559", "stderr": "", "stderr_lines": [], "stdout": "The Drush launcher could not find a local Drush in your Drupal site.\nPlease add Drush with Composer to your project.\nRun 'cd \"/var/www/drupalvm/drupal\" && composer require drush/drush'", "stdout_lines": ["The Drush launcher could not find a local Drush in your Drupal site.", "Please add Drush with Composer to your project.", "Run 'cd \"/var/www/drupalvm/drupal\" && composer require drush/drush'"]} I think we should add drush/drush as project dependency.