[K/JS] Prepare JS Plain Objects plugin to publication

plugins/js-plain-objects/compiler-plugin/testData/box/with-inheritance.kt

@@ -0,0 +1,28 @@
+package foo
+
+import kotlinx.js.JsPlainObject
+
+@JsPlainObject
+external interface User {
+    var name: String
+    val age: Int
+}
+
+@JsPlainObject
+external interface ExtendedUser : User {
+    val email: String
+}
+
+
+fun box(): String {
+    val user = ExtendedUser(name = "Name", age = 10, email = "test@test")
+
+    if (user.name != "Name") return "Fail: problem with `name` property"
+    if (user.age != 10) return "Fail: problem with `age` property"
+    if (user.email != "test@test") return "Fail: problem with `email` property"
+
+    val json = js("JSON.stringify(user)")
+    if (json != "{\"age\":10,\"name\":\"Name\",\"email\":\"test@test\"}") return "Fail: got the next json: $json"
+
+    return "OK"
+}