Add Nations Vs Players Game Mode (#2233)

## Description:
Fixes: #676 
This PR adds Players Vs Nations as a game mode in the menu.

For this change I have added two mutually exclusive option for this
mode:
1. Match number of nations to number of players who have joined
2. Set the number of nations to a fixed value

### Screenshots:
#### Options in Single player mode
<img width="1025" height="790" alt="image"
src="https://github.com/user-attachments/assets/c0685ea5-94f5-43c7-a9e5-390835fc94e9"
/>
<img width="1005" height="795" alt="image"
src="https://github.com/user-attachments/assets/dddba015-a424-40dd-a0fe-2571fd7b0fba"
/>

#### Options in lobby mode
<img width="1015" height="888" alt="image"
src="https://github.com/user-attachments/assets/45bc865b-c6a8-4b6a-9062-4eb499c1ea36"
/>

#### Example gameplay (1 Human Vs 90 Nations)
<img width="1888" height="912" alt="image"
src="https://github.com/user-attachments/assets/38faec75-171f-4358-a3be-93630cca1587"
/>


## Please complete the following:

- [X] I have added screenshots for all UI updates
- [X] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [X] I have added relevant tests to the test directory
- [X] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

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

saphereye

---------

Co-authored-by: Evan <evanpelle@gmail.com>

src/server/MapPlaylist.ts

@@ -7,6 +7,7 @@ import {
   GameMapType,
   GameMode,
   GameType,
+  HumansVsNations,
   Quads,
   Trios,
 } from "../core/game/Game";
@@ -67,6 +68,7 @@ const TEAM_COUNTS = [
   Duos,
   Trios,
   Quads,
+  HumansVsNations,
 ] as const satisfies TeamCountConfig[];
 
 export class MapPlaylist {
@@ -93,7 +95,7 @@ export class MapPlaylist {
       infiniteTroops: false,
       maxTimerValue: undefined,
       instantBuild: false,
-      disableNPCs: mode === GameMode.Team,
+      disableNPCs: mode === GameMode.Team && playerTeams !== HumansVsNations,
       gameMode: mode,
       playerTeams,
       bots: 400,