Added more docker jobs and apply same naming convention as build jobs

docker/gh-pages/Dockerfile

@@ -0,0 +1,12 @@
+FROM ruby:2.7
+
+ENV LC_ALL C.UTF-8
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US.UTF-8
+
+WORKDIR /usr/src/app
+
+COPY Gemfile just-the-docs.gemspec ./
+RUN gem install bundler && bundle install
+
+EXPOSE 4000

docker/gh-pages/docker-compose.yml

@@ -0,0 +1,14 @@
+version: "3.5"
+
+services:
+  jekyll:
+    build:
+      context: ../../docs
+      dockerfile: ./Dockerfile
+    ports:
+      - 4000:4000
+    volumes:
+      - ../../docs:/usr/src/app
+    stdin_open: true
+    tty: true
+    command: bundle exec jekyll serve -H 0.0.0.0 -t --force_polling