update link to plugin

[ikiwiki] / doc / todo / po:_translation_of_directives.mdwn

If a translated page contains a directive, it may expand to some english
text, or text in whatever single language ikiwiki is configured to "speak".

Maybe there could be a way to switch ikiwiki to speaking another language
when building a non-english page? Then the directives would get translated.

(We also will need this in order to use translated templates, when they are
available.)