Maven: Introduce test-js goal

#KT-7757 Fixed Maven K2JS should be able to build tests too

libraries/examples/js-example/src/test/kotlin/sample/SampleTest.kt

@@ -1,9 +1,11 @@
 package test.sample
 
+import sample.Hello
+
 import org.junit.Test
 
 class SampleTest {
     Test fun dummy(): Unit {
-
+        Hello().doSomething()
     }
-}
+}