only treat traffic_calming=island as an area tag

this is required for a proper fix of https://github.com/openstreetmap/id-tagging-schema/issues/733

modules/osm/tags.js

@@ -60,6 +60,9 @@ export var osmAreaKeysExceptions = {
         turntable: true,
         wash: true
     },
+    traffic_calming: {
+        island: true
+    },
     waterway: {
         dam: true
     }

modules/presets/index.js

@@ -305,6 +305,7 @@ export function presetIndex() {
       footway: true,
       railway: true,
       junction: true,
+      traffic_calming: true,
       type: true
     };
     let areaKeys = {};