Dynamic routing

Of course, no real app can live with only static URLs based on just pages, so let's add a bit of dynamic routing to our app:

1. Let's start with a small data source stub:

      // data/posts.js
      export default [
          {title: 'Foo'},
          {title: 'Bar'},
          {title: 'Baz'},
          {title: 'Qux'}
      ];

2. Now, let's connect it to our index page:

      // pages/index.js
      import React from 'react';
      import Link from "next/link";
      import Nav from "../components/Nav";
      import posts from "../data/posts";

      export default () => (
          <div>

              <Nav/>

              <hr/>

              <ul>
            {posts.map((post, index) => (
                <li key={index}>
                    <Link href...