Add themes

src/main/java/app/controllers/MenubarController.java

@@ -10,6 +10,7 @@ import com.google.common.eventbus.Subscribe;
 import app.events.ExitApplicationEvent;
 import app.events.LanguageChangedEvent;
 import app.events.OpenLinkInBrowserEvent;
+import app.events.ThemeChangedEvent;
 import app.events.ToggleCommentEvent;
 import app.events.ToggleWrapTextEvent;
 import javafx.event.ActionEvent;
@@ -107,6 +108,13 @@ public class MenubarController implements Initializable, Controller {
     this.eventBus.post(new ToggleWrapTextEvent(isSelected));
   }
 
+  @FXML
+  private void handleThemeChange(ActionEvent event) {
+    this.eventBus.post(
+      new ThemeChangedEvent(
+        ((RadioMenuItem) event.getSource()).getText()));
+  }
+
   /**
    * Handles the event where there was an exit request from the menu.
    * @param event