Improved local development with wrangler and workerd

This post announces Wrangler v3, which makes local-by-default development for Cloudflare Workers a reality by integrating Miniflare v3 powered by the open-sourced `workerd` runtime. This provides a more accurate local testing environment with significant performance improvements (10x faster startup, 60x faster script reloads). It details the architecture of Miniflare v3, its use of SQLite and a separate blob store for flexible storage, and the challenges and solutions for running unit tests within `workerd` processes using WebSockets and Node.js worker_threads. It also covers the effort to make `workerd` cross-platform, including Windows support using clang-cl and Bazel.