feat(card): add dataset hero image

Add the public hero image to the dataset card and store it under assets.

.gitattributes

@@ -2231,3 +2231,4 @@ wikidata/facts/zambia-latest.parquet filter=lfs diff=lfs merge=lfs -text
 wikipedia/documents/zimbabwe-latest.parquet filter=lfs diff=lfs merge=lfs -text
 wikipedia/sections/zimbabwe-latest.parquet filter=lfs diff=lfs merge=lfs -text
 wikidata/facts/zimbabwe-latest.parquet filter=lfs diff=lfs merge=lfs -text
+assets/dataset_hero.png filter=lfs diff=lfs merge=lfs -text

README.md

@@ -47,6 +47,8 @@ dataset_info:
 
 # NoeFlandre/osm-polygon-wikidata-only
 
+![NoeFlandre/osm-polygon-wikidata-only dataset overview](assets/dataset_hero.png)
+
 OSM polygons tagged with a `wikidata=*` reference, enriched with Wikipedia and Wikivoyage text across all available languages. The published tables are:
 
 - `polygons/<stem>.parquet` — one row per polygon