Add serialization plugin test with main-kts

libraries/tools/kotlin-main-kts-test/testData/hello-kotlinx-serialization.main.kts

@@ -0,0 +1,18 @@
+
+@file:Repository("https://jcenter.bintray.com/")
+@file:DependsOn("org.jetbrains.kotlinx:kotlinx-serialization-runtime:0.20.0-1.4.0-dev-5730", options = ["transitive=false"])
+
+import kotlinx.serialization.*
+import kotlinx.serialization.json.*
+
+@Serializable
+data class User(val firstName: String, val lastName: String)
+
+val json = Json(JsonConfiguration.Stable)
+
+val jsonData = json.stringify(User.serializer(), User("James", "Bond"))
+println(jsonData)
+
+val obj = json.parse(User.serializer(), """{"firstName":"James", "lastName":"Bond"}""")
+println(obj)
+