feat: add lychee for checking broken links

[Richard-Dang]

Pull Request Checklist

• Did you add new tests and confirm existing tests pass? (yarn test)
• Did you update relevant docs? (docs are found in the site folder, and guidelines for updating/adding docs can be found in the contribution guide)
• Do your commits follow the Conventional Commits standard?
• Does your PR title also follow the Conventional Commits standard?
• If you have a breaking change, is it correctly reflected in your commit message? (e.g. feat!: breaking change)
• Did you run lint (yarn lint:check) and fix any issues? (yarn lint:write)
• Did you follow the contribution guidelines?

---

PR-Codex overview

This PR primarily focuses on enhancing the documentation for Alchemy Smart Wallets by implementing Vale linting rules, updating existing content for clarity, and ensuring consistent terminology.

Detailed summary

• Added Vale configuration and style rules for documentation linting.
• Updated headings to title case in several .mdx files.
• Refined terminology for clarity (e.g., "DApp" to "DApp").
• Added new Vale rules for voice, tone, and code formatting.
• Improved documentation content for gas policy and migration guides.
• Added scripts for linting documentation and checking broken links in CI.

The following files were skipped due to too many changes: yarn.lock

✨ Ask PR-Codex anything about this PR by commenting with /codex {your question}

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Preview	Comments	Updated (UTC)
aa-sdk-ui-demo	Ready	Preview	Comment	Sep 11, 2025 5:55pm

[github-actions]

🌿 Documentation Preview

Name	Status	Preview	Updated (UTC)
Alchemy Docs	✅ Ready	🔗 Visit Preview	Sep 5, 2025, 9:10 PM

[Richard-Dang]

#2015