add a hint that creation_month takes a number, not a month name

[ikiwiki] / doc / plugins / edittemplate.mdwn

[[!template id=plugin name=edittemplate author="[[Joey]]"]]
[[!tag type/web]]

This plugin provides the [[ikiwiki/directive/edittemplate]] [[ikiwiki/directive]].
This directive allows registering [[template|templates]] pages, that
provide default content for new pages created using the web frontend.