Product monitoring: Create concepts page

We should document that we recommend a Prometheus Servicemonitor and point to the monitoring stack.
Mention that we label all Services accordingly, so users only need to deploy a Servicemonitor and get all metrics instantly.
Provide some nice screenshots from Prometheus

This is mostly done on https://docs.stackable.tech/home/stable/operators/monitoring/
Expand it with

• some screenshots from Prometheus
• link to the monitoring stack to showcase the setup

docs.stackable.tech/home/stable/operators/monitoring/ にある既存の monitoring ページから始め、現在のガイダンスを確認します。Prometheus のスクリーンショット、monitoring stack へのリンク、Prometheus ServiceMonitor をデプロイする推奨事項を追加します。セットアップとメトリクスの自動収集が明確に説明されていれば完了です。