feat(aio): copy example code from angular.io

aio/content/examples/cb-dependency-injection/ts/src/app/user.service.ts

@@ -0,0 +1,10 @@
+// #docregion
+import { Injectable } from '@angular/core';
+
+@Injectable()
+export class UserService {
+
+  getUserById(userId: number): any {
+    return {name: 'Bombasto', role: 'Admin'};
+  }
+}