Compatibility with Logitech Logi Options+: Fn keys

This was discovered when using an MX Keys keyboard with the “Logi Options+” software. While Karabiner Elements is running, the Logitech specific function keys (such as Fn-esc to toggle between function keys and media keys and f1, f2, f3 to switch between inputs) are not recognized.

The solution is to edit karabiner.json such that the "fn_function_keys" array is empty:

    "fn_function_keys": []

Credit: https://github.com/pqrs-org/Karabiner-Elements/issues/1450#issuecomment-1013932206