Run as non-root user for secure environments (#232)

Dockerfile

@@ -40,5 +40,8 @@ FROM scratch as scratch
 COPY --from=builder /redis_exporter /redis_exporter
 COPY --from=builder /etc/ssl/certs /etc/ssl/certs
+# Run as non-root user for secure environments
+USER 59000:59000
+
 EXPOSE     9121
 ENTRYPOINT [ "/redis_exporter" ]