Feature/spectral rule docs urls #21

[andreyyudin]

Closes #21

Summary

Add documentationUrl metadata to every Spectral rule so lint output can link directly to the rule guidance.

Changes Made

• Ruleset updates: added documentationUrl to every rule in .spectral.yaml, pointing at the corresponding docs/spectral-rules/ page.
• Spectral CLI guidance: updated CLI examples (e.g., docs/spectral-rules/index.md) to always pass --show-documentation-url, noting Spectral CLI 6.15.0+ is required to surface those links.
• Authoring guidelines: expanded contributor docs with instructions on choosing and validating documentation URLs for new rules.

Testing / Verification

• npx spectral lint example/example.1.0.0.oas.yml --show-documentation-url to confirm each violation now prints the expected link.
• Manually checked linked docs pages to ensure they exist and describe the referenced rules.

[github-actions]

Test Results

 1 files   8 suites   9s ⏱️
58 tests 58 ✅ 0 💤 0 ❌
59 runs  59 ✅ 0 💤 0 ❌

Results for commit 293d552.

♻️ This comment has been updated with latest results.

[github-actions]

🎉 Success! 🎉

PR successfully Fast Forward merged in ✅.