fix raspberry pi dockerfile: add missing runtime libs for pulseaudio & jackaudio backend

contrib/Dockerfile.Rpi

@@ -49,7 +49,7 @@ RUN cargo build --release --target arm-unknown-linux-gnueabihf --no-default-feat
 
 FROM resin/rpi-raspbian
 RUN apt-get update && \
-    apt-get install libasound2 && \
+    apt-get install libasound2 libpulse0 libjack0 && \
     rm -rf /var/lib/apt/lists/*
 
 RUN mkdir /librespot