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>

examples/HelloMod/HelloMod.csproj

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Beispiel-Mod für MSCO. Bauen: msbuild HelloMod.csproj -p:Configuration=Release
+  Ergebnis bin\Release\HelloMod.dll nach <Spielordner>\MSCO\Mods kopieren (oder auf dem Server nach data/mods).
+  GamePath anpassen, wenn My Summer Car woanders liegt.
+-->
+<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Release</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <OutputType>Library</OutputType>
+    <RootNamespace>HelloMod</RootNamespace>
+    <AssemblyName>HelloMod</AssemblyName>
+    <TargetFrameworkVersion>v3.5</TargetFrameworkVersion>
+    <TargetFrameworkProfile>Unity Full v3.5</TargetFrameworkProfile>
+    <LangVersion>13</LangVersion>
+    <OutputPath>bin\$(Configuration)\</OutputPath>
+    <DebugType>none</DebugType>
+    <Optimize>true</Optimize>
+    <GamePath Condition=" '$(GamePath)' == '' ">F:\SteamLibrary\steamapps\common\My Summer Car</GamePath>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="UnityEngine">
+      <HintPath>$(GamePath)\mysummercar_Data\Managed\UnityEngine.dll</HintPath>
+      <Private>False</Private>
+    </Reference>
+    <!-- MSCO selbst (die Mod-Schnittstelle MscoMod) -->
+    <Reference Include="MSCO">
+      <HintPath>$(GamePath)\MSCO\MSCO.dll</HintPath>
+      <Private>False</Private>
+    </Reference>
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="HelloMod.cs" />
+  </ItemGroup>
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+</Project>