This release includes a number of bug fixes and feature additions, it is a recommended update for all sites. Thanks to everyone who has helped with this release.
We're heavily using the responsive class field module in a custom project with a Bootstrap 4 theme and Paragraphs. Initial development took place outside of drupal.org's Git repositories. We feel confident to releasing our project's current version as alpha version at drupal.org and hope you'll find it useful in your Drupal site(s) as well.