The Hookdeck Vercel Middleware is a new feature that enables developers to turn any Vercel endpoint into an asynchronous endpoint with support for queuing, throttling, retry logic, delays, and verification. It allows developers to easily debug and build with webhooks and other asynchronous messaging use cases on Vercel. The middleware can be installed using npm i @hookdeck/vercel and requires a hookdeck.config.js file to be updated with configuration options. To get started, create a Hookdeck account, set environment variables for the API key and signing secret, deploy the project, and configure the middleware routes. The middleware is currently disabled in development environments but will be supported soon.