Update README files across all packages

[lpssformspree]

Summary

• Simplify root README with concise package descriptions, yarn-only install commands, and links to individual package READMEs
• Rewrite @formspree/ajax README with clearer bundler vs CDN quick start paths, complete default styles, and missing config options (projectId, useDefaultStyles)
• Add comprehensive @formspree/react README documenting useForm, useSubmit, ValidationError, FormspreeProvider, and extra data
• Add monorepo links, license section, and support links to all package READMEs

Test plan

• Verify all relative links between package READMEs resolve correctly
• Confirm code examples match current API signatures

🤖 Generated with Claude Code

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Latest commit: 1366760

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Project	Deployment	Actions	Updated (UTC)
formspree-react-demo	Ready	Preview, Comment	Apr 6, 2026 2:52pm