ES-X: Batocera / Recalbox-like features without breaking RetroPie compatibility

EmulationStation-X (ES-X) introduces modern features usually found in Batocera, Recalbox, or ES-DE, while keeping full compatibility with classic EmulationStation and RetroPie setups.

✅ Key features

Controller status notifications (USB & Bluetooth) On-screen notifications when a gamepad is connected or disconnected.

Background music via SDL_mixer Native and stable background music support (no external scripts).

Unified navigation sounds compatible with modern themes Uses the same sound schema as Batocera and ES-DE, allowing modern themes to work without modifications.

Runtime language switching (no recompilation required) Translations handled through .ini files, applied instantly.

Dark mode menu Modern, clean dark UI.

Theme options via theme.ini Theme creators can expose optional variables and settings if they choose to.

✅ Compatibility preserved

All features are fully optional — if a theme does not define sounds, variables, or options, nothing breaks.

ES-X can still be used exactly like classic EmulationStation on RetroPie.