[Feature-Request] Add support for setting --add-host

[ThaDaVos]

Currently, I've got a custom DNS running at home for giving out custom domain names for my services run at home - even though my host has as only DNS server my custom one, portainer somehow does not resolve these custom domains correctly if they are also defined externally (split-dns), to fix this I added the --add-host parameter to the portainer container, sadly this is not copied over to the compose-unpacker or even configurable, so it's having the same issues my current work around for this is running a while loop using a format script to get the RUN command for compose-unpacker container and adapt it with the --add-host parameters needed and run it manually but this is getting really cumbersome.

So, it would be great if the compose-unpacker copies the --network and --add-host parameters from the portainer container to fix this up.

Command I RUN:

while true; do docker inspect --format "$(curl -s https://gist.githubusercontent.com/efrecon/8ce9c75d518b6eb863f667442d7bc679/raw/run.tpl)" $(docker ps --quiet -f name=portainer-unpacker-*) && break; clear; sleep 1; done