Write a comparison to Kluent, AssertK, Strikt, Atrium, Kotest, other Kotlin assertion libraries?

They have various Kotlin-specific advantages. It would be good to understand what those are. Maybe someday we can provide some of them ourselves (though we haven't followed through on our Kotlin ambitions much yet).

\[edit: https://github.com/EventFahrplan/EventFahrplan/issues/141#issuecomment-491491046 was interested in this.\]

\[edit: One particular thing we should look into is whether those libraries support Kotlin multiplatform (KMP). I've heard that [Kotest](https://github.com/kotest/kotest) supports it, and it sounds like [Kluent has at least some support](https://github.com/MarkusAmshove/Kluent/issues/75#issuecomment-401538406).\]