Micronaut "Hello World" application

The corresponding article can be found at https://jonas-havers.de/articles/getting-started-with-micronaut/

Commands

• Run application with ./gradlew run (http://localhost:8888/hello/world)
• Run tests with ./gradlew test (build/reports/tests/test/index.html)
• Build executable JAR file with ./gradlew assemble (build/libs/helloworld-0.1-all.jar)