Add template for datagrid

[VincentLanglet]

Subject

I am targeting this branch, because it's a minor.

Fixed an error on SonataDoctrineORMAdminBundle:

ERROR: InvalidArgument - src/Builder/DatagridBuilder.php:150:71 - Argument 3 of Sonata\AdminBundle\Datagrid\Datagrid::__construct expects Sonata\AdminBundle\Datagrid\PagerInterface<Sonata\AdminBundle\Datagrid\ProxyQueryInterface>, Sonata\AdminBundle\Datagrid\PagerInterface<Sonata\DoctrineORMAdminBundle\Datagrid\ProxyQueryInterface> provided (see https://psalm.dev/004)
        return new Datagrid($admin->createQuery(), $admin->getList(), $pager, $formBuilder, $values);

Changelog

### Added
- Generics for Datagrid and DatagridInterface