geoserver: enable stac-datastore-plugin

https://docs.geoserver.org/latest/en/user/community/stac-datastore/index.html

Per @fmigneault request.

birdhouse/config/geoserver/default.env

@@ -23,7 +23,8 @@ export GEOSERVER_STABLE_EXTENSIONS="grib-plugin,netcdf-plugin,netcdf-out-plugin,
 # https://github.com/kartoza/docker-geoserver/blob/master/build_data/community_plugins.txt
 export GEOSERVER_COMMUNITY_EXTENSIONS="geopkg-plugin,\
 ogcapi-coverages-plugin,ogcapi-dggs-plugin,ogcapi-features-plugin,ogcapi-images-plugin,\
-ogcapi-maps-plugin,ogcapi-styles-plugin,ogcapi-tiled-features-plugin,ogcapi-tiles-plugin"
+ogcapi-maps-plugin,ogcapi-styles-plugin,ogcapi-tiled-features-plugin,ogcapi-tiles-plugin,\
+stac-datastore-plugin"
 
 # Must use single-quote for delayed eval.
 export GEOSERVER_DATA_DIR='${DATA_PERSIST_ROOT}/geoserver'