Add Flatpak support for Linux distributions #41
Description
Similar to #27, we should add Flatpak packaging for broader Linux distribution support.
Why:
- Universal package format works across all Linux distros (Debian, Fedora, Arch, etc.)
- Works on immutable distros like SteamOS (Steam Deck)
- Publish to Flathub for easy discovery and installation
- Sandboxed runtime with better security
Requirements:
- Add Flatpak maker/builder to Electron Forge config
- Create .desktop file for desktop integration
- Create .appdata.xml for metadata and screenshots
- Test on multiple distros (Fedora, Arch, Ubuntu, SteamOS)
- Submit to Flathub for official distribution
Related: #27 (added .deb support)
Done when:
- Users can install ROMie via Flatpak
- Package is available on Flathub
- Package appears in GitHub releases as fallback