Error: Class 'Crypt' not found

Problem/Motivation

Latest dev version gives error:
Error: Class 'Crypt' not found

Steps to reproduce

Install latest dev version with composer require 'drupal/colorbox:1.x-dev' and use it in a project.
Now open a page where colorbox is used.

Proposed resolution

Edit colorbox.theme.inc to include the used Crypt class.
Change it from:

use Drupal\file\Entity\File;
use Drupal\image\Entity\ImageStyle;

Into:

use Drupal\file\Entity\File;
use Drupal\image\Entity\ImageStyle;
use Drupal\Component\Utility\Crypt;