Environmental Variables for UID/GID

[thefirstofthe300]

I am running several docker containers for my media library and by default they all run with UID/GID of 99/100 (on my Fedora server, those are the nobody and user groups). I believe that environmental variables should be added to allow the user to change the UID/GID that Sonarr uses to allow the container to be more interoperable with other containers.