added favicon to website

Summary:
**Summary**

- flarnie kedromelon finishes up #965 by adding the favicon to the website
- thanks to kedromelon for the great favicon! 🎉

<img width="681" alt="screen shot 2017-11-22 at 11 58 00" src="https://user-images.githubusercontent.com/10538297/33140139-1c883108-cf7d-11e7-9ee6-da097eb32e29.png">

<img width="660" alt="screen shot 2017-11-22 at 11 57 46" src="https://user-images.githubusercontent.com/10538297/33140149-25071ccc-cf7d-11e7-8c49-043645f9294c.png">

**Test Plan**

- not applicable
Closes #1526

Reviewed By: flarnie

Differential Revision: D6976891

Pulled By: flarnie

fbshipit-source-id: 73a544ee6860f203361089e741007b93e8ba651e

Author: Michael Baldwin

website/core/Site.js

@@ -29,6 +29,14 @@ var Site = React.createClass({
           <meta property="og:url" content="http://draftjs.org/index.html" />
           <meta property="og:description" content="Rich Text Editor Framework for React" />
 
+          <link rel="apple-touch-icon" sizes="180x180" href="/img/apple-touch-icon.png" />
+          <link rel="icon" type="image/png" sizes="32x32" href="/img/favicon-32x32.png" />
+          <link rel="icon" type="image/png" sizes="16x16" href="/img/favicon-16x16.png" />
+          <link rel="manifest" href="/img/manifest.json" />
+          <link rel="mask-icon" href="/img/safari-pinned-tab.svg" color="#5bbad5" />
+          <link rel="shortcut icon" href="/img/favicon.ico" />
+          <meta name="msapplication-config" content="/img/browserconfig.xml" />
+          <meta name="theme-color" content="#852d2d" />
           <link rel="stylesheet" href="/css/draft.css" />
 
           <script type="text/javascript" src="//use.typekit.net/vqa1hcx.js"></script>

website/src/img/android-chrome-192x192.png

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<browserconfig>
+    <msapplication>
+        <tile>
+            <square150x150logo src="/img/mstile-150x150.png"/>
+            <TileColor>#da532c</TileColor>
+        </tile>
+    </msapplication>
+</browserconfig>

website/src/img/android-chrome-512x512.png

@@ -0,0 +1,18 @@
+{
+    "name": "",
+    "icons": [
+        {
+            "src": "/img/android-chrome-192x192.png",
+            "sizes": "192x192",
+            "type": "image/png"
+        },
+        {
+            "src": "/img/android-chrome-512x512.png",
+            "sizes": "512x512",
+            "type": "image/png"
+        }
+    ],
+    "theme_color": "#ffffff",
+    "background_color": "#ffffff",
+    "display": "standalone"
+}