add test files

js/js.translator/testFiles/extensionFunction/cases/extensionFunctionOnExpression.kt

@@ -0,0 +1,13 @@
+package foo
+
+fun Int.same() : Int {
+    return this
+}
+
+fun Int.quadruple() : Int {
+    return same() * 4;
+}
+
+fun box(): Boolean {
+    return ((3 + 4).quadruple() == 28)
+}