Add example of configuration arguments using Maven in Kotlin example

Nobody has claimed this yet.

Can we get added to the [`pom.xml`](https://github.com/mapstruct/mapstruct-examples/blob/master/mapstruct-kotlin/pom.xml) file in the [kotlin example](https://github.com/mapstruct/mapstruct-examples/tree/master/mapstruct-kotlin) some configuration arguments?

Right now I have the following and it's not working...because `kapt` is being used rather than the maven compiler plugin for annotation processing _(and after a lot of googling and searching, I can't find anything on how `kapt` processor args are meant to be formatted when using maven)_:

```xml
...


org.mapstruct
mapstruct-processor
${mapstruct.version}



-Amapstruct.defaultComponentModel=spring
-Amapstruct.unmappedTargetPolicy=IGNORE
-Amapstruct.suppressGeneratorTimestamp=true
-Amapstruct.suppressGeneratorVersionInfoComment=true

...
```

Start with mapstruct-kotlin/pom.xml and compare its annotation processor configuration with the requested MapStruct arguments. Verify the example's Maven configuration accepts the listed arguments and that the Kotlin example still builds successfully; done means the configuration is present as a usable example.

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