Add demo page for catch-all route feature

The /pages/shows/[...all].js page is a demo of the newly added
support for NextJS' catch-all routes feature:
https://nextjs.org/docs/routing/dynamic-routes#catch-all-routes

Support for this was introduced in next-on-netlify v1.1.0.

Author: FinnWoelm

pages/shows/[...params].js

@@ -0,0 +1,65 @@
+import fetch from 'isomorphic-unfetch'
+import Error from 'next/error'
+import Link from 'next/link'
+
+const CatchAll = ({ errorCode, show, params }) => {
+
+  // If show item was not found, render 404 page
+  if (errorCode) {
+    return <Error statusCode={errorCode} />
+  }
+
+  // Otherwise, render show
+  return (
+    <div>
+      <p>
+        This is a server-side rendered catch-all page. It catches all requests
+        made to /shows/:id/any/path/can/go/here... and makes those parameters
+        available in getInitialProps():
+        <br/>
+        {params.map((param, index) => (
+          <span key={index}>
+            [{index}]: {param}<br/>
+          </span>
+        ))}
+        <br/>
+        Refresh the page to see server-side rendering in action.
+        <br/>
+        You can also try changing the URL to something random,
+        such as /shows/{show.id}/whatever/path/you/want
+      </p>
+
+      <hr/>
+
+      <h1>Show #{show.id}</h1>
+      <p>
+        {show.name}
+      </p>
+
+      <hr/>
+
+      <Link href="/">
+        <a>Go back home</a>
+      </Link>
+    </div>
+  )
+}
+
+CatchAll.getInitialProps = async ({ res: req, query }) => {
+  // Get the params to render
+  const { params } = query
+
+  // Get the ID to render
+  const id = params[0]
+
+  // Get the data
+  const res = await fetch(`https://api.tvmaze.com/shows/${id}`);
+  const data = await res.json();
+
+  // Set error code if show item could not be found
+  const errorCode = res.status > 200 ? res.status : false
+
+  return { errorCode, show: data, params }
+}
+
+export default CatchAll