Add diagram-based example output

Author: seuros

.gitignore

@@ -7,7 +7,8 @@ Gemfile.lock
 InstalledFiles
 _yardoc
 coverage
-doc/
+doc/*
+!doc/switch.svg
 lib/bundler/man
 pkg
 rdoc

README.md

@@ -69,6 +69,16 @@ in the class.  The generated files will use an output filename of the format
 For examples of actual images generated using this task, see those under the
 examples folder.
 
+#### Example output
+
+Generate the sample diagram used in this README:
+
+```bash
+bundle exec ruby script/generate_example.rb
+```
+
+![Switch state machine](doc/switch.svg)
+
 ### Interactive graphs
 
 Jean Bovet's [Visual Automata Simulator](https://github.com/NimaGhaedsharafi/VAS)

doc/switch.svg

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require 'state_machines-diagram'
 require 'state_machines/graphviz'
 require 'state_machines/graphviz/renderer'