ci: Work on publishing a docker container

[laduke]

This is a first pass at making this into a docker. I've tested something similar in another repo, but this kind of thing always takes a couple tries -Getting CI to run correctly.

To test locally, you can do:
docker build . -t pylon -f Dockerfile
docker run --init -p 443:443 -p 19993:9993/udp -t pylon reflect
I'm sure this is fine though.
refract should work too, but I haven't practiced getting the args for that correct yet. Maybe we need to pass a file into the container for that to work?

I have README edits ready too, but will publish them later when we know things are working.

[laduke]

actually refract doesn't want to work in a container.

        pylon.cpp:001294:                     main: Address on network 6ab565387a123456 is 172.23.184.21
{
        "listen_addr":1.0.0.0,
        "listen_port":1080,
        "node_id":37d6e1336b,
        "net_id":6ab565387a442f6f
}
bind: Cannot assign requested address

Yeah I'm not sure. someone'll have to test on linux. Probably have to give it some permissions.

It's still worth doing if only for reflect.

edit: yeah it boots ok with host network and net cap admin

docker run --init -e ZT_PYLON_SECRET_KEY=$(cat identity.secret) -e ZT_PYLON_WHITELISTED_PORT=4545 \
--net=host --cap-add NET_ADMIN -t \
pylon refract 6ab565387a123456 --listen-addr 0.0.0.0 --listen-port 1080