The Bbutton is a package with 6 unique CSS animations for outline buttons from the Twitter Bootstrap 4 library. The package is simple and easy integrates into your project. The specification CSS Custom Properties uses for customization buttons, but also available a feedback for browsers which don’t support it (as IE 11).
The element is well documented, so setting it up couldn’t be tricky. For turning animation on you just need to add several classes to Bootstrap 4 button. CSS files of plugin, bootstrap.css v 4.0.0 and plugin docs with examples have included in archive already.