Feature Request - Environment variable for defaulting to dark theme

[librick]

Hey, great project! I'm working on setting up a media server using docker containers, and Doku is a great way for me to keep an eye on disk usage. My goal for my project is to allow anyone to spin up a media server with really good defaults.

I think it would be beneficial to have an environment variable/configuration option to control the default theme for Doku. I prefer the dark theme, but Doku currently defaults to the light theme. It'd be great if I could modify the environment of my docker-compose.yml file to tell Doku to start with the dark theme by default (i.e., with no user action).

Something like DOKU_THEME=<light|dark>. Then my docker-compose.yml file could look like:

  doku:
    image: amerkurev/doku:v0.0.16
    ports:
      - 9090:9090
    environment:
        DOKU_THEME=dark
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - /:/hostroot:ro

This pattern of declarative configuration using environment variables with the DOKU_ prefix is really powerful and I think would be useful for anyone who wants to run Doku in containers.

This is a really great project, thanks for contributing to open source!