Cannot resolve `spotify:prerelease:` context

[devgianlu]

The /context-resolve/v1/ endpoint does not seem capable of resolving spotify:prerelease: URIs, perhaps it needs to be replaced with something newer.

To reproduce:

• Start playing a track from a prereleased album on the official client
• Move to go-librespot 1 -> Works because the official client sends us the full context
• Try to move to go-librespot 2 -> Does not work because we try to resolve the context ourselves