Add token for invitation link url

Ah, the code is not in a ginvite.token.inc, but in ginvite.module.

  $tokens['register_link'] = [
    'name' => t('Register Link'),
    'description' => t('Url to register page with prefilled email address.'),
  ];
  $tokens['my_invitations_link'] = [
    'name' => t('My Invitations Link'),
    'description' => t('Url to user list of invitations.'),
  ];