kotlin-frontend-plugin | Gradle Kotlin plugin | Plugin library

I want to write a JavaScript library in Kotlin, using Gradle as the build tool with Kotlin as the config language for that, too. In the end I'd like to get a single JS file which can be used as a stand-alone library, i.e. with (all required parts of) the Kotlin library bundled into it.

What would a minimal setup to make this work look like? In particular, how do I get the Kotlin libraries bundled in?

Here is what I have so far.

https://kotlinlang.org/docs/tutorials/javascript/getting-started-gradle/getting-started-with-gradle.html
only uses Groovy to configure Gradle. It also uses the buildscript in combination with the apply plugin statement, where I was under the general impression that this is considered a legacy approach and the plugins section would be the preferred way.

https://kotlinlang.org/docs/reference/using-gradle.html#targeting-javascript
has Kotlin scripts. The code snippet for settings.gradle doesn't have a switch between Groovy and Kotlin, but it appears to work without modification in my settings.gradle.kts. That will create a file js/build/classes/kotlin/main/${project.name}.js which looks like this (with moduleKind = "commonjs"):