Explicitly specify volume in dockerfile

Author: NicoBiernat

Dockerfile

@@ -48,4 +48,5 @@ COPY --chown=app:app --from=compile-stage /app/beacon /beacon
 COPY --chown=app:app --from=compile-stage /app/static /static
 # copy the data folder with the correct permissions for the volume mount
 COPY --chown=app:app --from=compile-stage /app/data /data
+VOLUME /data
 ENTRYPOINT ["/beacon"]