chore: add OCI image labels to Dockerfile (prometheus#3593)

Signed-off-by: Julien Pivotto <291750+roidelapluie@users.noreply.github.com>

Author: roidelapluie

Dockerfile

@@ -2,6 +2,15 @@ ARG ARCH="amd64"
 ARG OS="linux"
 FROM quay.io/prometheus/busybox-${OS}-${ARCH}:latest
 LABEL maintainer="The Prometheus Authors <prometheus-developers@googlegroups.com>"
+LABEL org.opencontainers.image.authors="The Prometheus Authors"
+LABEL org.opencontainers.image.vendor="Prometheus"
+LABEL org.opencontainers.image.title="node_exporter"
+LABEL org.opencontainers.image.description="Prometheus exporter for hardware and OS metrics exposed by *NIX kernels"
+LABEL org.opencontainers.image.source="https://github.com/prometheus/node_exporter"
+LABEL org.opencontainers.image.url="https://github.com/prometheus/node_exporter"
+LABEL org.opencontainers.image.documentation="https://github.com/prometheus/node_exporter"
+LABEL org.opencontainers.image.licenses="Apache License 2.0"
+LABEL io.prometheus.image.variant="busybox"
 
 ARG ARCH="amd64"
 ARG OS="linux"