add a docker config

Dockerfile

@@ -0,0 +1,13 @@
+FROM ruby:2.7.2
+
+RUN bundle config --global frozen 1
+
+WORKDIR /usr/src/app
+
+COPY Gemfile Gemfile.lock ./
+RUN bundle install
+
+COPY . .
+
+
+CMD ["bundle", "exec", "middleman", "server"]

README.md

@@ -25,3 +25,12 @@ To build:
 To deploy on S3 (requires AWS credentials in `.s3.sync` in the yaml format):
 
     bundle exec middleman s3_sync
+
+## Using Docker
+
+Install Docker.
+
+```
+docker build . -t beoiwebsite
+docker run -it -p 4567:4567 --mount type=bind,source="$(pwd)",target=/usr/src/app beoiwebsite
+```