I think it would be great to use literalinclude for big code snippets,
because our IDEs could warn us about issues, and it would be easily to
showcase our coding standard. Before we do that though, let us validate
that it renders as expected. I have picked a complex example where we
have a configuration block.

Experiment with literalinclude

Fix PHPUnit deprecations

…ibute-of-discriminator-mapping

Allow classname in 'value' attribute of xml discriminator-mapping field

We use phpDocumentor/guides now, no need for this.

The last step was missing.