add:安装 Istio

[sunny0826]

提交 PR 后请先自查以下内容：

• PR 的标题格式为：在空白文档中新增内容 add: 文档标题，修改已有内容的文档 update：文档标题。
• 在该 PR 已指明解决的 issue 链接：https://github.com/servicemesher/istio-handbook/issues/92
• 已阅读并保证所提交 PR 符合写作规范。
• 文章内容格式请参考 PR add: practice/jwt-authorization #186。
• 保留下文中的声明。

声明

• 我认可本书的版权信息：本书著作权归属于 ServiceMesher 社区，我将保留对所修改内容的署名权。

• 我已阅读参与贡献说明，并加入了 istio-handbook-wg GitHub team。

[netlify[bot]]

Deploy preview for istio-handbook ready!

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https://deploy-preview-201--istio-handbook.netlify.app

[rootsongjc]

建议在开头就简明的写上环境依赖还有各个软件的版本。比如：

硬件要求

至少 2 核和 4G 的可用内存。

软件要求

1. minikube v1.9.2
2. istioctl v1.5.1
3. kubectl v1.18
4. docker 19.03.8

[mesher-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rootsongjc, sunny0826

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[mesher-bot]

New changes are detected. LGTM label has been removed.