Adapt docs on additional rules and dashboards

Makefile

README.md

build.sh

docs/developing-alerts-and-dashboards.md

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

docs/monitoring-external-etcd.md

examples/example-grafana-dashboard.json

examples/example.rules.yaml

...ples/grafana-additional-jsonnet-dashboard-example.jsonnet

...les/grafana-additional-rendered-dashboard-example.jsonnet

examples/jsonnet-build-snippet/build-snippet.jsonnet

examples/jsonnet-snippets/bootkube.jsonnet

examples/jsonnet-snippets/kubeadm.jsonnet

examples/jsonnet-snippets/node-ports.jsonnet

examples/ksonnet-example.jsonnet

examples/prometheus-additional-alert-rule-example.jsonnet

...ples/prometheus-additional-recording-rule-example.jsonnet

examples/prometheus-additional-rendered-rule-example.jsonnet

jsonnet/kube-prometheus/prometheus/prometheus.libsonnet

test.sh