Add support for event dispatcher priority

What's the rationale for setting the priority to "-900"?

vmarchuk → made their first commit to this issue’s fork.

@rszrama
This is something that can work https://git.drupalcode.org/project/commerce_email/-/merge_requests/12/diffs.
In this case, if the plugin is defined using a custom module, the priority parameter can be set directly from the plugin annotations (or, if not set, it will default to 0).
For plugins defined in the commerce_email module, the priority can be changed using hook_commerce_email_event_info_alter:

/**
 * Implements hook_commerce_email_event_info_alter().
 */
function hook_commerce_email_event_info_alter(&$definitions) {
  foreach ($definitions as &$definition) {
    if ($definition['id'] == 'order_paid') {
      $definition['priority'] = -900;
    }
  }
}

(we probably need to document this information in the README)

Change looks good at first glance!

Committed!

Automatically closed - issue fixed for 2 weeks with no activity.