Allow Margin on style for Activity Diagram

Question

Hello @PlantUML team, here is a wanted feature:

• Could you manage Margin on style for Activity Diagram?

@startuml
<style>
activityDiagram {
  activity {
    Padding 5
    Margin 30
  }
}
</style>
:a a a a a a;
:b b b b b b;
:a a a a a a;
@enduml

Padding seems to be OK. But not Margin... 

See also:

• https://forum.plantuml.net/11590/how-to-reduce-space-between-wbs-items

Thanks for your works...

If that can help,
Regards,
Th.