[ja] add figure/description in content/ja/docs/concepts/architecture/_index.md (#44917)

* update: content/ja/docs/concepts/architecture/_index.md

* update: L5

Co-authored-by: inukai <[email protected]>

---------

Co-authored-by: inukai <[email protected]>

Author: Okabe-Junya

content/ja/docs/concepts/architecture/_index.md

@@ -1,4 +1,8 @@
 ---
 title: "クラスターのアーキテクチャ"
 weight: 30
+description: >
+  Kubernetesの背後にあるアーキテクチャのコンセプト。
 ---
+
+{{< figure src="/images/docs/kubernetes-cluster-architecture.svg" alt="Components of Kubernetes" caption="Kubernetesクラスターのアーキテクチャ" class="diagram-large" >}}