add sample project in ruby on rails with postgres

Signed-off-by: Lukas Pol <lukaspaespol@gmail.com>

ruby_on_rails-postgres/Dockerfile

@@ -0,0 +1,26 @@
+FROM ruby:2.6.5
+
+# install nodejs / libdev / postgres-client
+RUN apt-get update -qq && apt-get install -y nodejs libpq-dev postgresql-client
+
+RUN mkdir /myapp
+WORKDIR /myapp
+COPY Gemfile /myapp/Gemfile
+COPY Gemfile.lock /myapp/Gemfile.lock
+
+##
+RUN gem install bundler:2.0.2
+RUN bundle install
+COPY . /myapp
+
+## install yarn
+RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - \
+    && echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list \
+    && apt-get update && apt-get install -y yarn && rm -rf /var/lib/apt/lists/*
+
+
+## Add Endpoint
+COPY entrypoint.sh /usr/bin/
+RUN chmod +x /usr/bin/entrypoint.sh
+ENTRYPOINT ["entrypoint.sh"]
+EXPOSE 3000