Add Docker Compose setup for local development

[2214962083]

Summary

Setting up a local development environment for a Cloudflare Workers project can be confusing for new contributors. A Docker Compose setup would provide a one-command development environment, lowering the barrier to contribution significantly.

Problem

New contributors need to:

1. Install Node.js with the correct version
2. Install and configure Wrangler
3. Set up local D1 databases and KV namespaces
4. Understand the Cloudflare Workers local dev workflow

This is a lot of steps, and any one of them can go wrong. A Docker Compose setup would eliminate most of these friction points.

Expected Behavior / Deliverable

• A docker-compose.yml (or compose.yml) file at the project root.
• A Dockerfile.dev for the development environment.
• Running docker compose up should:
  • Install all dependencies
  • Start the Wrangler dev server with local D1/KV emulation
  • Expose the app on a predictable port (e.g., localhost:8787)
  • Support hot-reload when source files change (volume mount)
• A CONTRIBUTING.md or updated README.md section documenting:
  • Prerequisites (Docker + Docker Compose)
  • How to start the dev environment
  • How to run tests inside the container
  • Common troubleshooting tips

Implementation Hints

• Project root contains package.json and wrangler.toml (or wrangler.jsonc) — these define the Worker configuration.
• Wrangler supports local development via wrangler dev --local which emulates D1/KV/R2 locally using Miniflare.
• The Dockerfile should be based on a Node.js image and run npm install + npx wrangler dev.
• Use volume mounts for src/ so changes are reflected without rebuilding.
• Environment variables can be passed via docker-compose.yml or a .env.example file.

Acceptance Criteria

• docker-compose.yml and Dockerfile.dev added to project root
• docker compose up starts a working dev environment
• Hot-reload works for source file changes
• Documentation added (CONTRIBUTING.md or README section)
• .env.example file with required environment variables documented