Improve Documentation for Android Kotlin DSL for protobuf-javalite

I'm having issue converting these gradle groovy code to kotlin dsl.
```
protobuf {
protoc {
artifact = 'com.google.protobuf:protoc:3.8.0'
}
generateProtoTasks {
all().each { task ->
task.builtins {
java {
option "lite"
}
}
}
}
}
```

**Especially the `option "lite"` in java block.**

Thanks.

Start from the Groovy protobuf configuration shown in the issue and identify the corresponding Android Kotlin DSL syntax, especially the `option "lite"` expression inside the Java block. Documentation is complete when it includes a working Kotlin DSL example for the full configuration and clearly shows how to enable the lite option.

Written by the indexing model from the issue text.