Kotlin/Multiplatform support

[jamiesanson]

The core of Konfigure, property-delegate based app configuration, is written in pure Kotlin. As such, Konfigure could be a good candidate for Kotlin/Multiplatform.

Kotlin/Multiplatform projects are in alpha, so we'd be a ways off implementing this in a stable release. However, we're able to make progress on this now and could have multiplatform support ready for when Kotlin/Multiplatform support goes stable.