lug-helper v2.9

Improvements & Fixes

• Updated to the latest RSI installer version
• Added basic support for NixOS
• Various improvements to terminal menu fallback mode
• Renamed --use-gui=[yes/no]/-g=[yes/no] command-line argument to --no-gui/-g
• No longer errors out if Lutris hasn't yet created certain directories
• Worked around Gitlab changing their API's URL formatting again
• Added a DLL override to the install json that disables powershell.exe. This allows the launcher to auto-update itself again

Other Changes

• Added some referral codes
• Minor code cleanup

Thanks to @LovingMelody for contributing to this release!