Please add a first-class entry to support Kotlin warnings.

Currently, tool java() picks up Kotlin warnings. While functional, this is hard to discover – a search for Kotlin support in this plugin yields nothing – and it makes for confusing Jenkinsfile code and build navigation ("Java Warnings") in pure Kotlin projects.

We'd expect to write recordIssues tool: kotlin() and find a menu entry "Kotlin Warnings".

Potentially related: gradle/kotlin-dsl#1031

Not sure how mixed-language projects should be handled.