Add support for `rodiojack` backend.

[agdphd]

The underlying librespot library already supports the JACK audio backend via rodio. Enabling it in spotifyd turns out to be dead simple--just needed to add the config enum elements to pass it through!

NOTE: I have tested this on my machine running Debian testing ("trixie"). The documentation for Fedora is based on the upstream docs for librespot: https://github.com/librespot-org/librespot/blob/329a1b16074af4d1a8abe2ed017b5d4a4a070ea1/COMPILING.md#audio-library-dependencies