Set init size to screen size

overworld.ts

@@ -128,6 +128,8 @@ namespace tiles {
     //% tilemap.fieldOptions.filter="tile"
     //% tilemap.fieldOptions.taggedTemplate="tilemap"
     //% tilemap.fieldOptions.tileWidth=8
+    //% tilemap.fieldOptions.initWidth=20
+    //% tilemap.fieldOptions.initHeight=15
     //% group="Creation" weight=49 blockGap=8
     //% duplicateShadowOnDrag
     export function createSmallMap(tilemap: tiles.TileMapData): WorldMap {