Caddy2 cloudflare plugin

[bugs181 (Levi Roberts)]

@balki

Compiling caddy with custom modules using docker.

docker run --rm -v `pwd`/output:/output caddy:builder sh -c "caddy-builder github.com/caddy-dns/cloudflare && cp /usr/bin/caddy /output/"

No need to checkout source or install go.

Is there any way we could get that to work in a docker compose file?