Wizard: add support of JS singleplatform projects

libraries/tools/new-project-wizard/resources/org/jetbrains/kotlin/tools/projectWizard/templates/simpleJsClient/TestClient.kt.vm

@@ -0,0 +1,12 @@
+import kotlin.browser.document
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class TestClient {
+    @Test
+    fun testSayHello() {
+        val container = document.createElement("div")
+        container.sayHello()
+        assertEquals("Hello from JS", container.textContent)
+    }
+} 

libraries/tools/new-project-wizard/resources/org/jetbrains/kotlin/tools/projectWizard/templates/simpleJsClient/client.kt.vm

@@ -1,14 +1,17 @@
 import kotlinx.html.div
 import kotlinx.html.dom.append
+import org.w3c.dom.Node
 import kotlin.browser.document
 import kotlin.browser.window
 
 fun main() {
-    window.onload = {
-        document.body?.append {
-            div {
-                +"Hello from JS"
-            }
+    window.onload = { document.body?.sayHello() }
+}
+
+fun Node.sayHello() {
+   append {
+        div {
+            +"Hello from JS"
         }
     }
 }