Include appendix about example error handling (#255)

Author: Girgias

manual.xml

@@ -426,6 +426,7 @@
  <book xml:id="appendices">
   <title>&Appendices;</title>
   &appendices.history;
+  &appendices.examples;
   &appendices.migration84;
   &appendices.migration83;
   &appendices.migration82;