Added jacoco to gradle build

simpleexample/build.gradle

 plugins {
+	// java application with main method
 	id 'application'
+	// use javafx modules
     id 'org.openjfx.javafxplugin' version '0.0.8'
+    
+	// test coverage
+    id 'jacoco'
 }
 
 repositories {
@@ -18,7 +23,7 @@ javafx {
 	version = '12'
     modules = [ 'javafx.controls', 'javafx.fxml' ]
     // run with --debug-jvm flag and
-    // launch debugger using Remove Java Application debug launch configuration
+    // launch debugger using Remote Java Application debug launch configuration
 }