Add a development section for contributors

This should make it easier for people to set up the library and run the test suite within Docker

Author: etagwerker

README.md

@@ -100,6 +100,18 @@ test:
   min_messages: WARNING
 </pre>
 
+## Development
+
+If you want to test this library locally, you can do so like this:
+
+```
+docker compose run --build --rm ruby /bin/bash
+bundle
+bundle exec rake
+```
+
+You will need Docker installed. The configuration is set up for the latest Ruby, Rails, Postgres, and MySQL versions.
+
 ## COPYRIGHT
 
 See [LICENSE](LICENSE) for details.