[K/JS] Add support of compilation with ES-classes

js/js.translator/testData/box/es6classes/savedInstanceInConstructor.js

@@ -0,0 +1,7 @@
+class JsFoo {
+    static instances = new Set();
+    constructor(value) {
+        this.value = value;
+        JsFoo.instances.add(this);
+    }
+}