Use native classes in app/router.js

packages/@ember/octane-addon-blueprint/files/tests/dummy/app/router.js

@@ -1,10 +1,10 @@
 import EmberRouter from '@ember/routing/router';
 import config from './config/environment';
 
-const Router = EmberRouter.extend({
-  location: config.locationType,
-  rootURL: config.rootURL
-});
+class Router extends EmberRouter {
+  location = config.locationType;
+  rootURL = config.rootURL;
+}
 
 Router.map(function() {
 });

packages/@ember/octane-app-blueprint/files/app/router.js

@@ -1,10 +1,10 @@
 import EmberRouter from '@ember/routing/router';
 import config from './config/environment';
 
-const Router = EmberRouter.extend({
-  location: config.locationType,
-  rootURL: config.rootURL
-});
+class Router extends EmberRouter {
+  location = config.locationType;
+  rootURL = config.rootURL;
+}
 
 Router.map(function() {
 });