Investigate how we could support Windows

Windows does not support virtual MIDI ports (see https://github.com/Boddlnagg/midir/issues/37), therefore users would have to install a custom MIDI loopback driver. We could e.g. add command-line options to configure custom MIDI input/output ports to connect to (instead of creating virtual ports). On Windows, these would be required, while on Unix-like platforms (macOS/Linux), they would be optional and default to the current behavior.