The albumsection directive is supplied by the album plugin.
The albumsection directive is used to split an album into sections. It can
only appear on a page that also has the album directive.
The filter parameter is a PageSpec against which viewer pages
are matched. The albumsection directive displays all the images that match
the filter, and the album directive displays any leftover images, like
this:
# Holiday photos
[[!album ]]
<!-- replaced with a list of any uncategorized photos; it will be
empty if they're all tagged as 'people' and/or 'landscapes' -->
## People
[[!albumsection filter="tagged(people)"]]
<!-- replaced with a list of photos tagged 'people', including
any that are also tagged 'landscapes' -->
## Landscapes
[[!albumsection filter="tagged(landscapes)"]]
<!-- replaced with a list of photos tagged 'landscapes', including
any that are also tagged 'people' -->