note about sort and dependency types

note about sort and dependency types

There's a gotcha where pagespec_match_list is used with a dependency type
that is not a full content dependency, and so ikiwiki does not know that
a content change to a page that sorted too low to match needs to trigger
a rebuild, since its sort order may have changed.

Inline is mostly ok re this, as it does use content dependencies. Except
for in the case of raw mode. But then, page metadata is documented to not
be loaded, so it doesn't make sense to use sortspecs that depend on
metadata. I hope. :)