[FEATURE] Make mounted folders paths configurable using environment variable

[mgite]

Currently we are mounting these folders when running container so that data is saved on disk. If one wants to use docker volumes currently you have to create 5 volumes each for each folder (appdata, audio, video, subscriptions, users) and mount them accordingly.

- /opt/youtube/appdata:/app/appdata
- /opt/youtube/audio:/app/audio
- /opt/youtube/video:/app/video
- /opt/youtube/subscriptions:/app/subscriptions
- /opt/youtube/users:/app/users

There are other files in /app so one can not create these folders inside volume and just mount it on /app. If there were environment variables to set PATH for these folders we would be able to mount this volume containing all these folders for example on /opt/data and then write env vars like this

APPDATA_PATH=/opt/data/appdata
AUDIO_PATH=/opt/data/audio
VIDEO_PATH=/opt/data/video
SUBSCRIPTIONS_PATH=/opt/data/subscriptions
USERS_PATH=/opt/data/users