Translate concepts/extend-kubernetes/extend-cluster/ into Japanese

[hasebe]

This is a...

• Feature Request
• Bug Report

Problem:
No concepts/concepts/extend-kubernetes/extend-cluster.md in Japanese.

Proposed Solution:
Copy a file from en contents to content/ja/docs/concepts/extend-kubernetes/extend-cluster.md and translate it into Japanese.

Page to Update:
https://kubernetes.io/ja/docs/concepts/extend-kubernetes/extend-cluster/

[hasebe]

/language ja

[hasebe]

/assign @hasebe

[sftim]

/priority backlog

[inductor]

/close

[k8s-ci-robot]

@inductor: Closing this issue.

In response to this:

/close

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.