update examples and regenerate manifests

README.md

docs/developing-prometheus-rules-and-grafana-dashboards.md

example.jsonnet

examples/kustomize.jsonnet

kustomization.yaml

manifests/blackbox-exporter-configuration.yaml

manifests/blackbox-exporter-deployment.yaml

manifests/blackbox-exporter-service.yaml

manifests/blackbox-exporter-serviceAccount.yaml

manifests/blackbox-exporter-serviceMonitor.yaml