add missing Monolog handler type in XML config
bug #4147 [Cookbook][Logging] add missing Monolog handler type in XML config (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

[Cookbook][Logging] add missing Monolog handler type in XML config

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets |

Omitting the type of a handler leads to an error:

> Symfony\Component\Config\Definition\Exception\InvalidConfigurationException: The child node "type" at path "monolog.handlers.swift" must be configured.

Commits
-------

dc33b0c add missing Monolog handler type in XML config