JS backend: added jsCode test cases

js/js.translator/testData/jsCode/cases/function.kt

@@ -0,0 +1,13 @@
+package foo
+
+fun callWithArgs(sumFunc: (Int, Int) -> Int, a: Int, b: Int): Int {
+    return sumFunc(a, b)
+}
+
+fun box(): String {
+    val kotlinSum: (Int, Int) -> Int = {(a, b) -> a + b}
+    val jsSum: (Int, Int) -> Int = js("function (a, b) { return a + b; }")
+    assertEquals(callWithArgs(kotlinSum, 1, 2), callWithArgs(jsSum, 1, 2))
+
+    return "OK"
+}