dsl: add Kotlin bus extensions

[lambdagg]

We might need something like:

import wtf.mizu.kawa.OptimizedBus

fun main() {
    val bus = OptimizedBus()

    bus.addListener { 
        on<String> {
            println(it)
        }
    }

    val event = "foobar123"
    bus.publish(event)
}

and

import wtf.mizu.kawa.OptimizedBus

fun main() {
    val bus = OptimizedBus()

    bus.addListener<String> { 
        println(it)
    }

    val event = "foobar123"
    bus.publish(event)
}

or name the function whatever we want, like buildListener as @xtrm-en told me but that wouldn't really make sense as we're not only building it but also adding it directly.

[lambdagg]

As of #7, I think we could actually be making the dsl an actual dsl-only project by wrapping our future Java implementation.

[qtdyn]

first of all, fuck you.
second of all, yes.