Add Plugin Support for mGBA Emulator

📋 Summary

Add official plugin support for mGBA, a fast, accurate Game Boy Advance emulator that also supports Game Boy, Game Boy Color, and e-Reader titles, allowing simple integration and setup within LaunchBox.

🎯 Feature Overview

• Auto-download and configure mGBA directly through LaunchBox.

• Recognize supported file formats and associate them with mGBA (e.g., .gba, .gb, .gbc).

• Offer built-in access to core emulator settings (video, audio, controls).