Add whitelist filter to Docker image

[RodolfoGS]

Is your feature request related to a problem? Please describe.
Hello, I'm trying to use the whitelist filter that is mentioned here, but from Docker:

  -wl ADDRESS [ADDRESS ...], --whitelist ADDRESS [ADDRESS ...]
                        Addresses of Bluetooth devices to allow, all other devices are ignored

Looks like that parameter is not included in the start.sh script that creates the conf file when the container starts.
https://github.com/theengs/gateway-docker/blob/main/chroot/opt/venv/start.sh

Describe the solution you'd like
A posibility to use WHITELIST environment variable with Docker.

[radim-kliment]

I implemented it here in PR:

theengs/gateway-docker#18