Add docker-compose.yml to simplify local setup

[SnickCH]

Hi

To simplify local setup and testing, I'd like to suggest adding a docker-compose.yml file to the project.

This would make it easier for others to:

• Run the server with minimal setup
• Ensure consistent environments across machines

Would you be open to including this in the repo?

• Here I added the labels for users that have watchtower in place.
• folder "data" in the directory of the docker-compose.yml for the mountpoint

services:
  dumbkan:
    image: dumbwareio/dumbkan:latest
    restart: unless-stopped
    ports:
      - "3000:3000"
    volumes:
      - ./data:/app/data
    labels:
      - "com.centurylinklabs.watchtower.enable=true"

Thanks!