plugins: Install the heatmap plugin at version 0.0.4

Make the plugin available for downstream. The version appears
to be signed. Assuming the signature is checked at install time
and that versions can't be changed.

Dockerfile.ubi8

@@ -137,6 +137,9 @@ COPY --from=go-src /tmp/grafana/bin/grafana* /tmp/grafana/bin/*/grafana* ./bin/
 COPY --from=js-src /tmp/grafana/public ./public
 COPY --from=go-src /tmp/grafana/LICENSE ./
 
+USER grafana
+RUN grafana cli plugins install neocat-cal-heatmap-panel 0.0.4
+
 EXPOSE 3000
 
 ARG RUN_SH=./packaging/docker/run.sh