Facilitate external review of the new Dokka Gradle DSL document

[IgnatBeresnev]

After the internal review is done (#3538), the document should be reviewed by the Kotlin Build Tooling team, to validate the ideas and the feasibility.

Some other people from the Kotlin team can participate in the review as well - there's no predefined list, but we can ask Sergey (the maintainer of kotlinx.cover) and some other people who are proficient with Gradle.