Add ENV variables for Volume mapping

[bigred10151990]

I wanted to see if it was possible to add the volume mapping to the ENV variables. I have written a Home Assistant app for Listenarr but HA Apps to not allow for users to change the docker files so they are not able to set their own volume mappings in the app. this causes the app data to remain in the default non persistent Docker volume and so data is wiped out on an update of the app.