Add `junit5-jupiter-starter-maven-scala` sample.

[daggerok]

Overview

This PR contains junit5-jupiter-starter-maven-scala sample with minimal configuration for getting started project with JUnit Jupiter using Maven build system and Scala programming language.

---

I hereby agree to the terms of the JUnit Contributor License Agreement.

[daggerok]

please review

[sormuras]

Superseded by

• https://github.com/junit-team/junit5-samples/pull/190

Using sbt with Scala seems more natural to me.