Created by: cvrebert
Based on @pete-otaqui's work from #11851.
Per @mdo's feedback in that issue, this makes it an experiment rather than integrating the feature into Bootstrap itself.
Also renamed the class to .row-eq-height and removed the screen size variants, as I don't quite get what the use-case is for those (and this just keeps things simple).
(An actual screenshot image of the example needs to be added.)