I would like to extend the Stamen Toner map style (https://github.com/stamen/toner-carto/) with a layer to render piers (Way:area,manmade=pierman_made=pier).
I managed to install tilemill on Ubuntu (https://tilemill-project.github.io/tilemill/docs/linux-install/) and also was able to render the resulting XML style with a separate Mapnik install (https://switch2osm.org/serving-tiles/manually-building-a-tile-server-ubuntu-22-04-lts/).
The layer definitions / postgis queries seem to be made in https://github.com/stamen/toner-carto/blob/master/toner.yml
What would be the correct entry to create a piers
layer and style it with e.g.
#piers{
line-width: 0.25;
polygon-fill: @color_physical_bright;
line-color: @color_administrative_lowzoom;
}