Add MapVisual support (#85)

https://docs.screeps.com/api/#Game-map-visual

Author: Zomis

src/jsMain/kotlin/screeps/api/Game.kt

@@ -112,6 +112,7 @@ external object Game {
         fun isRoomAvailable(roomName: String): Boolean
         fun getRoomTerrain(roomName: String): Room.Terrain
         fun getRoomStatus(roomName: String): RoomStatusResult
+        val visual: MapVisual
 
         interface RouteResult {
             val exit: ExitConstant

src/jsMain/kotlin/screeps/api/MapVisual.kt

@@ -0,0 +1,13 @@
+package screeps.api
+
+import screeps.api.RoomVisual.*
+
+external interface MapVisual {
+    fun line(start: RoomPosition, end: RoomPosition, style: LineStyle = definedExternally): MapVisual
+    fun circle(pos: RoomPosition, style: CircleStyle = definedExternally): MapVisual
+    fun rect(topLeftPosition: RoomPosition, width: Double, height: Double, style: ShapeStyle = definedExternally): MapVisual
+    fun poly(points: Array<RoomPosition>, style: ShapeStyle = definedExternally): MapVisual
+    fun text(text: String, position: RoomPosition, style: TextStyle = definedExternally): MapVisual
+    fun clear(): MapVisual
+    fun getSize(): Double
+}