[K/JS] Support companion objects in external and exported declarations

js/js.translator/testData/box/jsExport/interfaceWithCompanion.js

@@ -0,0 +1,12 @@
+$kotlin_test_internal$.beginModule();
+
+module.exports = function() {
+    var { A } = require("main").api
+
+    return {
+        "res": A.ok()
+    };
+};
+
+$kotlin_test_internal$.endModule("lib");
+

js/js.translator/testData/box/jsExport/interfaceWithCompanion.kt

@@ -0,0 +1,24 @@
+// MODULE_KIND: COMMON_JS
+// SKIP_MINIFICATION
+
+// FILE: api.kt
+package api
+
+@JsExport
+interface A {
+    companion object {
+        fun ok() = "OK"
+    }
+}
+
+// FILE: main.kt
+external interface JsResult {
+    val res: String
+}
+
+@JsModule("lib")
+external fun jsBox(): JsResult
+
+fun box(): String {
+    return jsBox().res
+}