Export workflow chart to SVG

It should be encouraged to use SVG since SVG is better format suited for vector graphics and widely supported now.

Author: analogic

workflow/dumping-workflows.rst

@@ -4,17 +4,17 @@
 How to Dump Workflows
 =====================
 
-To help you debug your workflows, you can dump a representation of your workflow with
-the use of a ``DumperInterface``. Use the ``GraphvizDumper`` to create a
-PNG image of the workflow defined above::
+To help you debug your workflows, you can dump a representation of your workflow
+with the use of a ``DumperInterface``. Use the ``GraphvizDumper`` to create a
+SVG image of the workflow defined above::
 
     // dump-graph.php
     $dumper = new GraphvizDumper();
     echo $dumper->dump($definition);
 
 .. code-block:: terminal
 
-    $ php dump-graph.php | dot -Tpng -o graph.png
+    $ php dump-graph.php | dot -Tsvg -o graph.svg
 
 The result will look like this:
 
@@ -25,7 +25,7 @@ with the ``WorkflowDumpCommand``:
 
 .. code-block:: terminal
 
-    $ php bin/console workflow:dump name | dot -Tpng -o graph.png
+    $ php bin/console workflow:dump name | dot -Tsvg -o graph.svg
 
 .. note::