introduce experimental scala-api

[robstoll]

Platform (all, jvm, js, android): scala
Extension (none, kotlin 1.3): none

Code related feature

some code is already committed but we have not yet created an artifact so far. The following things need to be done in addition

• rename atrium-scala to atrium-scala2 as we are most likely going to use atrium-scala for Scala 3
• create a bundle module
• setup publishing for atrium-scala2
• use atrium-logic instead of domain-builders
• adjust issue templates, include scala as platform (maybe rename platform to something else?)