Install biber in the CI image so the paper's bibliography builds

Dockerfile

@@ -8,6 +8,7 @@ RUN chmod -R 777 /tmp
 RUN apt-get update
 RUN apt-get upgrade -y
 RUN TZ=America/Los_Angeles DEBIAN_FRONTEND=noninteractive apt-get install -y \
+    biber \
     build-essential \
     ccache \
     clang \