add version_added attribute to module docs.

library/cloud/ec2_vol

@@ -40,6 +40,7 @@ options:
     required: false
     default: 100
     aliases: []
+    version_added: "1.3"
   device_name:
     description:
       - device id to override device mapping. Assumes /dev/sdf for Linux/UNIX and /dev/xvdf for Windows.