【Documentation】improve docs about extensions

[zhuxiujuan28]

1. 快速入门：按照 v3.4 补充 3 篇文档。https://deploy-preview-3208--kubesphere-website.netlify.app/zh/docs/v4.1/02-quickstart/05-deploy-wordpress/
2. 快速入门：优化安装组件文档。https://deploy-preview-3208--kubesphere-website.netlify.app/zh/docs/v4.1/02-quickstart/02-install-an-extension/
3. 扩展组件管理指南：优化安装组件文档。https://deploy-preview-3208--kubesphere-website.netlify.app/zh/docs/v4.1/06-extension-user-guide/01-install-components/
4. 扩展组件使用指南：加一节概述。https://deploy-preview-3208--kubesphere-website.netlify.app/zh/docs/v4.1/11-use-extensions/00-overview/

[netlify[bot]]

✅ Deploy Preview for kubesphere-website ready!

Built without sensitive environment variables

Name	Link
🔨 Latest commit	ca8c3e74083a6bb8be75dc0c742502a54f69897f
🔍 Latest deploy log	https://app.netlify.com/sites/kubesphere-website/deploys/672c5d2bd7fa95000822c0ac
😎 Deploy Preview	https://deploy-preview-3208--kubesphere-website.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[zhuxiujuan28]

/assign @zheng1 please review and merge this pr

[zheng1]

/approve /lgtm

[ks-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: zheng1, zhuxiujuan28

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/kubesphere/website/blob/master/OWNERS)~~ [zheng1] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment