Document how to create ECK objects programmatically

This structure is a starting point.

use Drupal\eck\Entity\EckEntity;

$organization = EckEntity::create([
  'entity_type' => $eck_entity_type,
  'type' => $eck_entity_bundle,
]);
$organization->setOwner($account);
$organization->set('title', $the_title);
$organization->set('field_some_string', $something);
$organization->save();