docs: palette page & start docs playground

[hehehai]

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

Solution

How is the change tested?

Changelog

Type	Component	Changelog(CN)	Changelog(EN)	Related issues
docs	docs	新增色板页面	add palette page	-
docs	docs	快速上手演示DEMO	start page playground demo	-
docs	global docs	代码块边距	code block pading	-

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

🤖 修改均参照 React Arco Docs