create TUN device in startup script if specified

[rvaidya]

lifted from https://github.com/haugene/docker-transmission-openvpn/

with this, you don't need to run the container in privileged mode or mount the tun device from the host - you just need to add the NET_ADMIN capability:

ex:

  jackett:
    cap_add:
      - NET_ADMIN
    image: dyonr/jackettvpn:latest
    container_name: jackett

[apeman76]

bump please implement this. this docker is perfect but this would make it even perfecterder

[rvaidya]

bump please implement this. this docker is perfect but this would make it even perfecterder

I've pushed this to docker hub if you want to use it in the short term until the PR is merged docker pull rvaidya/jackettvpn:latest