Fix the issues reported by phpcs

   /**
+   * Get the result from a handled message envelope.
+   *
    * @param \Symfony\Component\Messenger\Envelope $envelope
+   *   The message envelope.
    *
    * @return mixed
+   *   The result from handling the message.

The verb used in the description must be declined to the third person singular.

The result from handling the message. is a bit too broad. The description should say exactly what is returned, especially when there are values returned in case of errors.

Fixes the issue providing patch.
Please review.

-Messenger must be downloaded with Composer, and can be installed like any other Drupal module.
+Messenger must be downloaded with Composer,
+and can be installed like any other Drupal module.

That line has been split too early, given that without exceeding 80 characters, the first line would be Messenger must be downloaded with Composer, and can be installed like any.

 /**
- *
+ * Class to provide functionality for MessengerDataCollector.

Saying that a class provides functionality for itself is not an helpful description, and it is also wrong since a class provides functionality to every class and function that uses it.

 /**
- *
+ * A trait to provides method to extract the result from Symfony Messenger.
  */
 trait ResponseTrait {

That description is quite vague too.

+   * Retrieves the result from a Symfony Messenger envelope.
+   *
    * @param \Symfony\Component\Messenger\Envelope $envelope
+   *   The envelope containing the message result.
    *
    * @return mixed
+   *   The result of the message handling.

The result of the message handling. is not quiet different from The result from handling the message. If the latter is a bit too vague, the first is a bit too vague too. At least, it should say what exactly is returned.

Addressed #4. Updated patch.