Create CONTRIBUTING.md with contribution guidelines

Added guidelines for contributing to the project.

Author: katiesavage

CONTRIBUTING.md

@@ -0,0 +1,17 @@
+## Contributing
+
+[fork]: https://github.com/github/REPO/fork
+[pr]: https://github.com/github/REPO/compare
+[style]: https://github.com/styleguide/ruby
+
+Hi there! We're thrilled that you'd like to contribute to this project. Your help is essential for keeping it great.
+
+Contributions to this project are [released](https://help.github.com/articles/github-terms-of-service/#6-contributions-under-repository-license) to the public under the [project's open source license](LICENSE).
+
+Please note that this project is released with a [Contributor Code of Conduct](CODE_OF_CONDUCT.md). By participating in this project you agree to abide by its terms.
+
+## Resources
+
+- [How to Contribute to Open Source](https://opensource.guide/how-to-contribute/)
+- [Using Pull Requests](https://help.github.com/articles/about-pull-requests/)
+- [GitHub Help](https://help.github.com)