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

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
+}