Customizable Traefik host port

Allow users to free up port 80 on the host machine, without losing
Traefik's Docker routing super-powers.

lib/mrsk/commands/traefik.rb

@@ -4,7 +4,7 @@ class Mrsk::Commands::Traefik < Mrsk::Commands::Base
       "--detach",
       "--restart", "unless-stopped",
       "--log-opt", "max-size=#{MAX_LOG_SIZE}",
-      "--publish", "80:80",
+      "--publish", port,
       "--volume", "/var/run/docker.sock:/var/run/docker.sock",
       "traefik",
       "--providers.docker",
@@ -45,6 +45,10 @@ class Mrsk::Commands::Traefik < Mrsk::Commands::Base
     docker :image, :prune, "--all", "--force", "--filter", "label=org.opencontainers.image.title=Traefik"
   end
 
+  def port
+    "#{config.raw_config.traefik.fetch("host_port", "80")}:80"
+  end
+
   private
     def cmd_args
       (config.raw_config.dig(:traefik, "args") || { }).collect { |(key, value)| [ "--#{key}", value ] }.flatten