Add a dockerfile for easy development (#9)

Signed-off-by: Andrew Kofink <akofink@redhat.com>

Author: akofink

Dockerfile

@@ -0,0 +1,15 @@
+# docker build . -t openscap_parser # build the container image
+# docker run -itv $PWD:/app:z openscap_parser rake # run tests
+# docker run -itv $PWD:/app:z openscap_parser pry --gem # console
+
+FROM ruby:2.5
+
+RUN gem update bundler
+
+WORKDIR /app
+
+COPY . ./
+
+RUN bundle -j4
+
+CMD bash

README.md

@@ -41,6 +41,16 @@ After checking out the repo, run `bin/setup` to install dependencies. Then, run
 
 To install this gem onto your local machine, run `bundle exec rake install`. To release a new version, update the version number in `version.rb`, and then run `bundle exec rake release`, which will create a git tag for the version, push git commits and tags, and push the `.gem` file to [rubygems.org](https://rubygems.org).
 
+### With Docker
+
+A Dockerfile is provided to allow a containerized development environment:
+
+```
+docker build . -t openscap_parser # build the container image
+docker run -itv $PWD:/app:z openscap_parser rake # run tests
+docker run -itv $PWD:/app:z openscap_parser pry --gem # console
+```
+
 ## Contributing
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/elobato/openscap_parser. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [Contributor Covenant](http://contributor-covenant.org) code of conduct.