Add Plugin Support for Mednaffen Emulator

📋 Summary

Introduce official plugin support for Mednafen, a highly accurate multi-system emulator that supports platforms like PS1, TurboGrafx-16, Sega Saturn, and more. This would streamline setup and game management across multiple systems within LaunchBox.

🎯 Feature Overview

This plugin would:

• Automatically download and configure Mednafen inside LaunchBox.

• Provide per-system configuration options (e.g. BIOS, core settings, input) through the emulator panel.

• Allow for easy importing and launching of supported systems with pre-mapped platform defaults.

• Optionally support integration with Mednaffe (GUI front-end) for advanced users.