Fix a TS error when using Inngest in projects with `composite` setting

[MonsterDeveloper]

Summary

Adds some type exports to index.ts that fix a TS error in composite projects.

Checklist

• [ ] Added a docs PR that references this PR N/A
• [ ] Added unit/integration tests N/A
• [x] Added changesets if applicable

Related

Fixes #384

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: e9e4c60012806f6718c2688d0ebb5551f316d16d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | ------- | ----- | | inngest | Patch |

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[jpwilliams]

Absolute star, @MonsterDeveloper 🙂 Thanks for this

[jpwilliams]

Released in kbd>[inngest@3.4.3](https://github.com/inngest/inngest-js/releases/tag/inngest%403.4.3)</kbd.