Beef up the example inventory

Signed-off-by: martin f. krafft <madduck@madduck.net>
diff --git a/examples/classes/mail/init.yml b/examples/classes/mail/init.yml
new file mode 100644
index 0000000..8751beb
--- /dev/null
+++ b/examples/classes/mail/init.yml
@@ -0,0 +1,2 @@
+applications:
+  - postfix