use main annotation

The main annotation is more idiomatic, otherwise the package object becomes the main class.

Author: bishabosha

src/main/g8/src/main/scala/Main.scala

@@ -1,4 +1,4 @@
-def main(args: Array[String]): Unit = {
+@main def Hello: Unit = {
     println("Hello world!")
     println(msg)
 }