add "supermarket" POI layer

layers/config/tree.js

@@ -146,6 +146,7 @@ BR.confLayers.tree = {
                 'health_food',
                 'ice_cream_shop',
                 'organic',
+                'supermarket',
             ]
         },
         'tourism': [

layers/overpass/shop/food/supermarket.geojson

@@ -0,0 +1,12 @@
+{
+    "geometry": null,
+    "properties": {
+        "name": "Supermarket",
+        "id": "supermarket",
+        "overlay": true,
+        "dataSource": "OverpassAPI",
+        "icon": "fas-shopping-basket",
+        "query": "nwr[shop=supermarket];"
+    },
+    "type": "Feature"
+}