Added Britannia map with 23 NPC as well as their flags (#186)

Let me know if you have any questions or concerns. This is my first time
near coding, so it would not hurt to double check my work. Thanks!

src/client/components/Maps.ts

@@ -15,6 +15,7 @@ export const MapDescription: Record<keyof typeof GameMapType, string> = {
   Asia: "Asia",
   Mars: "Mars",
   SouthAmerica: "South America",
+  Britannia: "Britannia",
 };
 
 @customElement("map-display")

src/client/utilities/Maps.ts

@@ -8,6 +8,7 @@ import blackSea from "../../../resources/maps/BlackSea.png";
 import africa from "../../../resources/maps/Africa.png";
 import asia from "../../../resources/maps/Asia.png";
 import mars from "../../../resources/maps/Mars.png";
+import britannia from "../../../resources/maps/Britannia.png";
 
 import { GameMapType } from "../../core/game/Game";
 
@@ -33,6 +34,8 @@ export function getMapsImage(map: GameMapType): string {
       return asia;
     case GameMapType.Mars:
       return mars;
+    case GameMapType.Britannia:
+      return britannia;
     default:
       return "";
   }

src/core/game/Game.ts

@@ -49,6 +49,7 @@ export enum GameMapType {
   Africa = "Africa",
   Asia = "Asia",
   Mars = "Mars",
+  Britannia = "Britannia",
 }
 
 export enum GameType {

src/core/game/TerrainMapFileLoader.ts

@@ -34,6 +34,7 @@ const MAP_FILE_NAMES: Record<GameMapType, string> = {
   [GameMapType.Asia]: "Asia",
   [GameMapType.Mars]: "Mars",
   [GameMapType.SouthAmerica]: "SouthAmerica",
+  [GameMapType.Britannia]: "Britannia",
 };
 
 class GameMapLoader {