feat(stepper): 补充步进器相关文档与类型描述

[kiner-tang]

这个 PR 做了什么? (简要描述所做更改)

• feat: 补充步进器相关文档与类型描述

这个 PR 是什么类型? (至少选择一个)

• [ ] 错误修复(Bugfix) fix #{issue id}
• [ ] 新功能(Feature) resolve #{issue id}
• [ ] 代码重构(Refactor)
• [X] 文档修改(Docs)
• [ ] 代码风格更新(Code style update)
• [X] 类型描述更新(TypeScript definition update)
• [ ] 其他，请描述(Other, please describe):

这个 PR 涉及以下平台:

• [ ] 未涉及平台修改
• [X] 所有小程序
• [ ] 微信小程序
• [ ] 支付宝小程序
• [ ] 百度小程序
• [ ] 字节跳动小程序
• [ ] QQ 轻应用
• [ ] 京东小程序
• [ ] 快应用平台（QuickApp）
• [ ] Web 平台（H5）
• [ ] 移动端（React-Native）

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: f7e29a5e533ce0671938b1ded61be0793f06c8e8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

| Name | Type | | --------- | ----- | | ossaui | Patch | | ossa-demo | Patch | | ossa-doc | Patch |

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[vercel[bot]]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Updated
ossa-demo	❌ Failed (Inspect)		Nov 27, 2022 at 1:48AM (UTC)
ossa-doc	✅ Ready (Inspect)	Visit Preview	Nov 27, 2022 at 1:48AM (UTC)