docs: add business funnel demo and related docs

[LofiSu]

[中文版模板 / Chinese template]

🤔 This is a Demo add business funnel demo and related docs

• [ ] New feature
• [ ] Bug fix
• [ ] TypeScript definition update
• [ ] Bundle size optimization
• [ ] Performance optimization
• [ ] Enhancement feature
• [ ] Refactoring
• [ ] Update dependency
• [ ] Code style optimization
• [ ] Test Case
• [ ] Branch merge
• [ ] Release
• [ ] Site / documentation update
• [ √] Demo update
• [ ] Workflow
• [ ] Other (about what?)

🔗 Related issue link

🔗 Related PR link

https://github.com/VisActor/VChart/issues/2657

🐞 Bugserver case id

💡 Background and solution

📝 Changelog

Language	Changelog
🇺🇸 English
🇨🇳 Chinese

☑️ Self-Check before Merge

⚠️ Please check all items below before requesting a reviewing. ⚠️

• [ ] Doc is updated/provided or not needed
• [ ] Demo is updated/provided or not needed
• [ ] TypeScript definition is updated/provided or not needed
• [ ] Changelog is provided or not needed

---

🚀 Summary

copilot:summary

🔍 Walkthrough

copilot:walkthrough

[xiaoluoHe]

效率非常高👍，有几个问题还再仔细看一下：

1. 跨层文字布局还是有问题：
   • 文字没有在矩形内居中
   • 图表宽度调小一些，文字重叠问题比较严重
   • 一个矩形内的 3 行文字，建议用 1 个 richtext 就可以了，省的要写 3 个 text 图元
2. 文字最好计算一下 maxLength，在空间不够的时候，可以自动省略；