Add automated validation scripts for links and image locations

[torimwhaley]

Summary

Adds automated validation scripts that run on PRs to help maintain documentation quality. These checks are informational only and will not block merging.

Changes

New Scripts

• scripts/check-image-locations.js - Validates that images follow the repository structure (e.g., guides/dashboard.mdx → images/guides/dashboard/)
• .github/workflows/validate-docs.yml - GitHub Actions workflow that runs validation on every PR

Updated Scripts

• scripts/check-links.js - Now also validates redirect destinations in docs.json to catch broken redirects when pages are moved

What This Does

When a PR is opened, the workflow automatically:

1. ✅ Checks for broken internal links
2. ✅ Validates image locations match page structure
3. ✅ Verifies redirect destinations exist
4. ✅ Identifies orphaned pages not in docs.json

Important: These checks show as ⚠️ warnings and provide helpful feedback, but will NOT block PR merging.

Notes

• Pre-existing issues (49 misplaced images, 6 broken links) are from the recent repo reorganization and can be fixed separately (in seperate PR)
• This automation prevents new issues from being introduced going forward

[github-actions]

📋 Documentation Validation Report

⚠️ Some issues were found in this PR. These are informational warnings and will not block merging.

🔗 Links

❌ Found broken links (click to expand)

📄 Found 154 documentation files
📄 guides/embedding/dashboards.mdx:447
   🔗 Broken link: /references/user-attributes
📄 guides/table-calculations.mdx:6
   🔗 Broken link: references/dimensions
📄 guides/table-calculations.mdx:6
   🔗 Broken link: references/metrics
📄 guides/table-calculations.mdx:27
   🔗 Broken link: references/metrics
📄 references/iframe-embedding.mdx:337

🖼️ Images

❌ Found image location issues (click to expand)

📄 Found 153 documentation files
   📄 get-started/develop-in-lightdash/adding-tables-to-lightdash.mdx:162
      ❌ Expected in: images/get-started/develop-in-lightdash/adding-tables-to-lightdash/
   📄 get-started/exploring-data/exploring-your-content.mdx:127
      ❌ Expected in: images/get-started/exploring-data/exploring-your-content/
   📄 get-started/exploring-data/using-explores.mdx:110
      ❌ Expected in: images/get-started/exploring-data/using-explores/
   📄 guides/cli/how-to-use-lightdash-validate.mdx:37
      ❌ Expected in: images/guides/cli/how-to-use-lightdash-validate/
   📄 guides/developer/cli/how-to-compile-your-lightdash-project.mdx:20

---

💡 Quick Reference:

• A page at guides/dashboard.mdx should use images from images/guides/dashboard/
• Shared images can be placed in parent directories
• All internal links must point to existing files

📖 Run node scripts/check-links.js and node scripts/check-image-locations.js locally for full details.