Use Runtime API Interface

[johnny-woodtke]

Description

Addresses the issue: https://github.com/vercel-community/bun/issues/1

I essentially just copied over my repo containing the Bun runtime implemented via Vercel's Runtime API.

However, the following files are not exactly the same:

• example/api/index.ts (uses a simpler request handler)
• example/package.json (removed Elysia as a dependency)
• example/vercel.json (uses [email protected] instead of @godsreveal/[email protected])
• src/build.ts (updated the User-Agent header for the bun binary download)
• .gitignore (used this project's and ignored the dist directory)
• package.json (used this project's, added some required fields, a description, and incremented the version)
• README.md (used this project's, updated the serverless function structure, added GH integration, updated manual deployment)

Recommended Deployment Procedure

1. Publish new version of package.
2. Verify Vercel preview deployment downloads this package, builds, and deploys successfully.
3. Verify /api route works correctly at preview deployment.
4. Merge this PR to main.