Add BepInEx6 IL2CPP support

[ManlyMarco]

No description provided.

[Copilot]

Pull Request Overview

Adds support for BepInEx v6 IL2CPP runtime by creating a separate IL2CPP-compatible project while maintaining BepInEx v5 support. The PR introduces shared code structure to avoid duplication and updates existing code to be compatible with both versions.

• Restructures the solution to support both BepInEx v5 (Mono) and v6 (IL2CPP) builds
• Creates shared code project to minimize duplication between the two builds
• Implements IL2CPP-specific utilities and compatibility layer for Unity integration

Reviewed Changes

Copilot reviewed 15 out of 21 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
nuget.config	Adds BepInEx package source for dependencies
README.md	Updates installation instructions to mention both BepInEx versions
FPSCounter_Shared/.	Creates shared project structure with common code
FPSCounter_IL2CPP/.	New IL2CPP-compatible implementation with specialized utilities
FPSCounter/.	Refactors existing BepInEx v5 project to use shared code
*.sln, Directory.Build.props	Updates build configuration for multi-project structure

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