Add Redis accessory

[nicogaldamez]

Why

• Many users rely on Redis as a core dependency in their projects.

What

• The Redis accessory should be optional
• Add a new toggle "Include a Redis accessory" under Accessories section
• When enabled, display the following input fields:
  • image: defaults to redis:latest
  • port: defaults to 6379
  • roles: defaults to web. Allow multiple roles
  • cmd: defaults to /bin/sh -c 'redis-server --requirepass $REDIS_PASSWORD'

Once configured, the final output should look like this:

redis:
    image: redis:latest
    port: 6379
    roles:
      - web
      - job
    cmd: "/bin/sh -c 'redis-server --requirepass $REDIS_PASSWORD'"
    volumes:
      - /var/lib/redis:/data
    env:
      secret:
        - REDIS_PASSWORD

Volumes and env could be added automatically.