Add Kotlin Serialization Support

**Is your feature request related to a problem? Please describe.**

For people who want to use the Kotlin codegeneration and also use Kotlin serialization, annotations need to be used. As is, only reflective kotlin parsing frameworks can be used.

**Describe the solution you'd like**

Add an option to the kotlin codegen that enables inclusion of these annotations.

**Describe alternatives you've considered**

The kotlin serialization plugin only offers generated serializers as an alternative to its own generated serializers, which would require substantially more code generation (and not be that great anyway).

**Additional context**

I'm a user of kotlin multiplatform, where kotlin serialization works but the Java-only JSON parsing choices do not, so it solves a problem for me.