feat: support placeholder and zIndex props

[anlyyao]

🤔 这个 PR 的性质是？

• 日常 bug 修复
• 新特性提交
• 文档改进
• 演示代码改进
• 组件样式/交互改进
• CI/CD 改进
• 重构
• 代码风格优化
• 测试用例
• 分支合并
• 其他

🔗 相关 Issue

相关 PRs

TDesignOteam/tdesign-api#787
Tencent/tdesign-common#2367

reference from: Tencent/tdesign-mobile-vue#2103

💡 需求背景和解决方案

📝 更新日志

• feat(Navbar): 新增 placeholder 属性，默认值为 false；新增 zIndex 属性，默认值为 1

• feat(TabBar): 新增 placeholder 属性，默认值为 false；新增 zIndex 属性，默认值为 1

• 本条 PR 不需要纳入 Changelog

☑️ 请求合并前的自查清单

⚠️ 请自检并全部勾选全部选项。⚠️

• 文档已补充或无须补充
• 代码演示已提供或无须提供
• TypeScript 定义已补充或无须补充
• Changelog 已提供或无须提供

[pkg-pr-new]

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npm i https://pkg.pr.new/tdesign-mobile-react@852

commit: 96163da

[github-actions]

[codecov-commenter]

Codecov Report

❌ Patch coverage is 75.34247% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.77%. Comparing base (02b774b) to head (96163da).
⚠️ Report is 363 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/hooks/useElementHeight.ts	51.72%	14 Missing ⚠️
src/tab-bar/TabBar.tsx	82.35%	3 Missing ⚠️
src/navbar/Navbar.tsx	96.15%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           develop     #852       +/-   ##
============================================
+ Coverage     6.93%   56.77%   +49.83%     
============================================
  Files          400      288      -112     
  Lines         4241     7363     +3122     
  Branches       990     1987      +997     
============================================
+ Hits           294     4180     +3886     
+ Misses        3947     3183      -764     

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