[docs] Add React SPA demos to repo and site (#179)

* Home section around over-prefetching.

* Over-prefetching partial.

* Changing carousel by content.

* Adding link to React SPA demo to repo and site.

* Shorter version of Glitch git URL.

demos/spa/README.md

@@ -0,0 +1,15 @@
+# Demo: Quicklink integration for create-react-app
+A demo showing how to use Quicklink with in a create-react-app site.
+To integrate your React SPA with Quicklink, follow the steps [here](/~https://github.com/GoogleChromeLabs/quicklink#single-page-apps-react).
+
+## Glitch Source
+* [Link to Glitch App](https://create-react-app-quicklink.glitch.me/)
+* [Link to Project on Glitch](https://glitch.com/~create-react-app-quicklink)
+
+## Installation
+```
+git clone https://api.glitch.com/git/create-react-app-quicklink
+npm install
+npm start
+npm run build
+```

site/src/demo.njk

@@ -13,6 +13,8 @@ sections:
         -
           description: A demo showing how to use Quicklink with Workbox for offline caching and links in the visible viewport.
           link: "* [Using Quicklink with Service Workers (via Workbox)](/~https://github.com/GoogleChromeLabs/quicklink/tree/master/demos/news-workbox)"
+        - description: A demo showing how to integrate Quicklink with create-react-app.
+          link: "* [Using Quicklink in a React single-page app](/~https://github.com/GoogleChromeLabs/quicklink/tree/master/demos/spa)"
 ---
 {% extends "layouts/normal-section-wrapper.njk" %}
 {% block section %}