Feat: allow users to change dotenv file with env var

[JoaoCostaIFG]

This facilitates the usage of docker secrets for the keys/tokens.

For example on a docker-compose.yml file:

muse:
  image: codetheweb/muse:latest
  container_name: muse
  secrets:
    - muse_env
  environment:
    - ENV_FILE=/run/secrets/muse_env
  restart: unless-stopped
  
secrets:
  muse_env:
    file: /usr/local/etc/muse_env

See relevant dotenv doc

• I updated the changelog

[JoaoCostaIFG]

Not sure if I should update the changelog. Please let me know.

[github-actions]

📦 A new release has been made for this pull request.

To play around with this PR, pull codetheweb/muse:pr-1040 or codetheweb/muse:3d7a85843fc4c8028ac87a0e5df98c477f2fffc1.

Images are available for x86_64 and ARM64.

Latest commit: 3d7a858

[codetheweb]

Cool!

1. Let's default ENV_FILE to /config in the Dockerfile so there's a sensible default.
2. We should also document this in the README.

Thank you!