docs(space): 新增关于space子元素key的FQA

[czq297297]

Types of changes

• [ ] New feature
• [ ] Bug fix
• [ ] Enhancement
• [ ] Component style change
• [ ] Typescript definition change
• [ ] Documentation change
• [ ] Coding style change
• [ ] Refactoring
• [ ] Test cases
• [ ] Continuous integration
• [ ] Breaking change
• [ ] Others

Background and context

#1220 #1223

Solution

How is the change tested?

Changelog

Component	Changelog(CN)	Changelog(EN)	Related issues
Space	文档新增keyFAQ	文档增加keyFAQ

Checklist:

• [ ] Test suite passes (npm run test)
• [ ] Provide changelog for relevant changes (e.g. bug fixes and new features) if applicable.
• [ ] Changes are submitted to the appropriate branch (e.g. features should be submitted to feature branch and others should be submitted to main branch)

Other information