Introducing workerd: the Open Source Workers runtime

Introduced workerd, an open-source runtime based on the same code powering Cloudflare Workers. workerd is designed for self-hosting Workers applications, realistic local development and testing (integrating with Miniflare and Wrangler), and programmable proxies. It emphasizes a server-first, event-driven architecture, web standard APIs, nanoservices (running multiple Workers isolates within a single process for low-latency communication), homogeneous deployment (running every service on every machine), and capability bindings for cleaner configuration and SSRF safety.