Add docker image (#375)

* Add Dockerfile

Add documentation

Ref #375

* Add PORT, VOLUME and reduce size of the docker image significantly

Fix doc and reduce image size

Fix #375

* Fix docker compose

substrate/docker/cleanup.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+# This script helps reduce the size of the built image
+# It removes data that is not required.
+
+export PATH=$PATH:$HOME/.cargo/bin
+
+cargo clean
+rm -rf /root/.cargo /root/.rustup /tmp/*