add support for building=supermarket in value dropdown

Author: matkoniecz

data/fields/building.json

@@ -57,6 +57,7 @@
             "stable": "Stable",
             "stadium": "Stadium Building",
             "static_caravan": "Mobile Home",
+            "supermarket": "Supermarket Building",
             "sty": "Pigsty",
             "synagogue": "Synagogue Building",
             "temple": "Temple Building",