Support Kotlin Multiplatform

[samoylenkodmitry]

We have to make a decision to use Moshi or write our custom Protobuf *.proto -> to Kotlin's serialization data models *.kt codegenerator.
However, we want to be open to switching to Multiplatform in the future.

Do Moshi's team have a KMM in their roadmap?

[JakeWharton]

No one is working on this library so I would not rely on this happening. The conversation to Kotlin/JVM (#1252) stalled, and that's a prerequisite.