Document applying the plugin when using Gradle's Kotlin DSL

[d-noll]

What is your use-case and why do you need this feature?

I was trying to use kotlinx.serialization from a Gradle build script which is not the main build script.

So far, I have verified that this is legal:

buildscript {
    dependencies {
        val kotlinVersion = "1.5.31"
        classpath(kotlin("gradle-plugin", version = kotlinVersion))
        classpath(kotlin("serialization", version = kotlinVersion))
    }
}

The documentation for applying it for Groovy in Kotlin syntax ends up as this:

apply(plugin = "gradle-plugin")
apply(plugin = "kotlinx-serialization")

But this fails the build with:

* What went wrong:
Plugin with id 'gradle-plugin' not found.

The documentation describes this as "the old way", but the new way documented doesn't work unless you're in the main build file, which I am not.

Describe the solution you'd like

• Documentation gives a working example of how to apply the plugin for Gradle Kotlin DSL.
• Documentation does not use the wording "the old way" unless it also describes a newer alternative which works in files which are not the main build script.