Add about feature

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

@@ -9,6 +9,7 @@ import com.google.common.eventbus.Subscribe;
 
 import app.events.ExitApplicationEvent;
 import app.events.LanguageChangedEvent;
+import app.events.OpenLinkInBrowserEvent;
 import app.events.ToggleCommentEvent;
 import javafx.event.ActionEvent;
 import javafx.fxml.FXML;
@@ -120,6 +121,11 @@ public class MenubarController implements Initializable, Controller {
   /*                                   ABOUT                                  */
   /* ------------------------------------------------------------------------ */
 
+  @FXML
+  private void handleAbout(ActionEvent event) {
+    String aboutLink = "https://gitlab.stud.idi.ntnu.no/oysteikt/tdt4100-project-2021v/-/blob/master/README.md";
+    this.eventBus.post(new OpenLinkInBrowserEvent(aboutLink));
+  }
 
   /* ------------------------------------------------------------------------ */
   /*                               SUBSCRIPTIONS                              */