[JS IR] Add stdlib regression tests

js/js.translator/testData/box/regression/stdlibTestSnippets/json.kt

@@ -0,0 +1,13 @@
+// EXPECTED_REACHABLE_NODES: 1274
+// KJS_WITH_FULL_RUNTIME
+
+import kotlin.js.json
+
+fun box(): String {
+    var obj = json(Pair("firstName", "John"), Pair("lastName", "Doe"), Pair("age", 30))
+    assertEquals("John", obj["firstName"], "firstName")
+    assertEquals("Doe", obj["lastName"], "lastName")
+    assertEquals(30, obj["age"], "age")
+
+    return "OK"
+}