Add tutorial files.

Dockerfile

@@ -0,0 +1,17 @@
+FROM ruby:2.5
+RUN apt-get update -qq && apt-get install -y nodejs postgresql-client
+RUN mkdir /myapp
+WORKDIR /myapp
+COPY Gemfile /myapp/Gemfile
+COPY Gemfile.lock /myapp/Gemfile.lock
+RUN bundle install
+COPY . /myapp
+
+# Add a script to be executed every time the container starts.
+COPY entrypoint.sh /usr/bin/
+    RUN chmod +x /usr/bin/entrypoint.sh
+ENTRYPOINT ["entrypoint.sh"]
+EXPOSE 3000
+
+# Start the main process.
+CMD ["rails", "server", "-b", "0.0.0.0"]