feat: implement default url serializer

modules/@angular/router/src/url_tree.ts

@@ -0,0 +1,11 @@
+import { Tree, TreeNode } from './tree';
+
+export class UrlTree extends Tree<UrlSegment> {
+  constructor(root: TreeNode<UrlSegment>, public queryParameters: {[key: string]: string}, public fragment: string | null) {
+    super(root);
+  }
+}
+
+export class UrlSegment {
+  constructor(public segment: any, public parameters: {[key: string]: string}) {}
+}