Add category to singleplayer (#449)

## Description:
Just simply adds categories to the single player menu
![Screenshot 2025-04-11 at 05 40
49](https://github.com/user-attachments/assets/e6811b69-5abf-427f-9989-55f4538b034f)

Fixes #453 

## Please complete the following:

- [X] I have added screenshots for all UI updates
- [X] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [X] I understand that submitting code with bugs that could have been
caught through manual testing blocks releases and new features for all
contributors

## Please put your Discord username so you can be contacted if a bug or
regression is found:

lunhuiyan1718

src/core/game/Game.ts

@@ -70,6 +70,29 @@ export enum GameMapType {
   FaroeIslands = "FaroeIslands",
 }
 
+export const mapCategories: Record<string, GameMapType[]> = {
+  continental: [
+    GameMapType.World,
+    GameMapType.NorthAmerica,
+    GameMapType.SouthAmerica,
+    GameMapType.Europe,
+    GameMapType.Asia,
+    GameMapType.Africa,
+    GameMapType.Oceania,
+  ],
+  regional: [
+    GameMapType.BlackSea,
+    GameMapType.Britannia,
+    GameMapType.GatewayToTheAtlantic,
+    GameMapType.BetweenTwoSeas,
+    GameMapType.Iceland,
+    GameMapType.Japan,
+    GameMapType.Mena,
+    GameMapType.Australia,
+  ],
+  fantasy: [GameMapType.Pangaea, GameMapType.Mars, GameMapType.KnownWorld],
+};
+
 export enum GameType {
   Singleplayer = "Singleplayer",
   Public = "Public",