MSCO 2.10.0: mod support, ESC no longer quits from the main menu

- MscoMod API (ModApi.cs) and ModLoader: own mods from MSCO\Mods, hooks for menu/game/update/GUI,
  session and player events, Send/OnMessage between players (MsgType.ModMessage)
- Server mods: ModList before Welcome, consent prompt (INSTALL & JOIN), download with SHA-256 check
  into MSCO\Mods\Servers, active only on that server; game start waits for the download
- Mods page in the MSCO menu, console command "mods"
- Server browser: MODS pill, VANILLA/MODDED filters, mod list in the server profile
- PlayMaker ApplicationQuit is ignored in the main menu (ESC used to close the game)
- MODDING.md and examples/HelloMod

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

MSCO.cs

@@ -11,7 +11,7 @@ namespace MSCO
         /// Version der Mod. Kleine Updates: nur die dritte Stelle erhöhen (2.9.1, 2.9.2 ...) - sie bleiben mit
         /// Servern und Mitspielern derselben ersten zwei Stellen kompatibel.
         /// </summary>
-        public const string ModVersion = "2.9.1";
+        public const string ModVersion = "2.10.0";
         /// <summary>
         /// Netzwerk-Version (die ersten beiden Stellen). Nur erhöhen, wenn sich das Protokoll inkompatibel ändert - dann
         /// auch GameServer.ModVersion im Server.