bugfix: Exporting types for hierarchical layout

[tyler27]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features) - No test required for this, just exporting the types for hierarchical.
• Docs have been added / updated (for bug fixes / features) - Not required

PR Type

Exporting hierarchical layout types to fix the missing type declaration issue:

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

There is no exported members for the hierarchical layout, forcing user's to create their own type if they want to use the hierarchical layout.

Issue Number: N/A

What is the new behavior?

Exporting hierarchical type.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

Very minor change, literally one line. Just need to export the hierarchical layout type.

If for whatever reason this was a specific design decision, please let me know.

[netlify]

✅ Deploy Preview for reagraph ready!

Name	Link
🔨 Latest commit	ff38353
🔍 Latest deploy log	https://app.netlify.com/sites/reagraph/deploys/67c883d4eca63800094b53a0
😎 Deploy Preview	https://deploy-preview-310--reagraph.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.