docs: declare explicit viewer configs (marketplace/retail)

README.md

@@ -7,6 +7,17 @@ tags:
   - smartphones
   - regression
 license: cc-by-4.0
+# Viewer configs: two flat parquet files, one config each (keeps the
+# auto-viewer from concatenating them into one null-padded table)
+configs:
+- config_name: marketplace_listings
+  data_files:
+  - split: train
+    path: marketplace_listings.parquet
+- config_name: retail_listings
+  data_files:
+  - split: train
+    path: retail_listings.parquet
 ---
 
 # DZ Smartphone Pricing (Algeria)