Add `librespot_options` option

[DarkMatterMatt]

This PR adds support for adding arbitrary additional librespot options. It's completely opt-in and does not change any existing behaviour

Some users may wish to change librespot settings, and many won't have the time to fluff around cloning repos and adding options to suit their use case. This is a minimal effort way to enable advanced users to use any option in while using the addon.

See the librespot documentation for more information about other options

---

To test this option:

1. Enable debug logging; we'll check that the settings are being correctly set by reading the logs
2. Change the value in the config, e.g. --volume-ctrl fixed --normalisation-pregain -9
3. Save changes & restart the addon
4. View the logs, see sample output below

Sample output

[2024-04-06T12:31:32Z INFO  librespot] librespot 0.4.2 UNKNOWN (Built on 2024-04-01, Build ID: YwHEteUz, Profile: release)
[2024-04-06T12:31:32Z TRACE librespot] Command line argument(s):
[2024-04-06T12:31:32Z TRACE librespot] 		bitrate "320"
[2024-04-06T12:31:32Z TRACE librespot] 		name "Home Assistant"
[2024-04-06T12:31:32Z TRACE librespot] 		disable-audio-cache
[2024-04-06T12:31:32Z TRACE librespot] 		verbose
[2024-04-06T12:31:32Z TRACE librespot] 		volume-ctrl "fixed"
[2024-04-06T12:31:32Z TRACE librespot] 		normalisation-pregain "-9"
[2024-04-06T12:31:32Z DEBUG librespot_discovery::server] Zeroconf server listening on 0.0.0.0:43321