Allow user and group mapping

[ghost]

• I am running the latest version
• I checked the documentation and found no answer
• I checked to make sure that this issue has not already been filed

Problem Description

I'm running the AdguardHome docker image, with the conf and work dirs mapped to local folders. Adguard creates files within these folders as root. I would like the option to map to another user, the way linuxserver.io images do: https://docs.linuxserver.io/general/understanding-puid-and-pgid

Proposed Solution

Allow for PUID and PGID environment variables to be set, so that files written by AdguardHome will map to the user I specify, so that I don't run into permission issues.

Alternatives Considered

Another option would be for me to use docker's built in --user flag:

https://docs.docker.com/engine/reference/run/

But for that to work the processes within the container would have to be able to cope with running as a different user, and not as root. I'm not sure if that's currently the case, and did not see anything in the documentation about that.

edit: By the way, my compliments on the project, really nice to use and works like a charm!