Fixing Docusaurus migration issues

Summary:
**Summary**

Fixes #1765

Includes:
1. Upgrading Docusaurus to 1.1.0, which fix the sticky footer issue.
2. Using production assets (for react, react-dom, immutable, babel-core) instead of development ones.
3. Supporting small screens with css.

More details in the issue.

**Test Plan**

Live site with the fixes: https://noamelb.github.io/draft-js

* Wide desktop:
![screencapture-noamelb-github-io-draft-js-2018-05-21-22_50_02](https://user-images.githubusercontent.com/7422547/40327618-45d38ba4-5d4c-11e8-908a-0f04a30a4d2c.png)

* Mobile:
![screencapture-noamelb-github-io-draft-js-2018-05-21-22_58_13](https://user-images.githubusercontent.com/7422547/40328208-4635f60c-5d4e-11e8-8838-5e2ee125e2a6.png)

* Mobile Docs:
![screencapture-noamelb-github-io-draft-js-docs-getting-started-html-2018-05-21-23_09_18](https://user-images.githubusercontent.com/7422547/40328215-49b5034a-5d4e-11e8-8166-152dfa161dcf.png)
Closes #1771

Reviewed By: yangshun

Differential Revision: D8095846

Pulled By: yangshun

fbshipit-source-id: a07720785d787a6455c2704b2f4413b0572af321

Author: NoamELB

website/package.json

@@ -9,7 +9,7 @@
     "rename-version": "docusaurus-rename-version"
   },
   "devDependencies": {
-    "docusaurus": "1.0.15"
+    "docusaurus": "1.1.3"
   },
   "dependencies": {
     "babel-preset-env": "1.6.0",

website/pages/en/index.js

@@ -254,11 +254,11 @@ class Index extends React.Component {
             <p>
               In Draft.js, everything is customizable &ndash; we provide the
               building blocks so that you have full control over the user
-              interface. Here's a simple example of a rich text editor built in
-              Draft.js:
+              interface. <span className="hide-on-mobile">Here's a simple example of a rich text editor built in
+              Draft.js:</span>
             </p>
 
-            <div id="rich-example"></div>
+            <div className="hide-on-mobile" id="rich-example"></div>
           </section>
 
           <section className="home-bottom-section">
@@ -268,10 +268,10 @@ class Index extends React.Component {
           </section>
         </section>
 
-        <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.0.1/react.js"></script>
-        <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.0.1/react-dom.js"></script>
-        <script src="https://cdnjs.cloudflare.com/ajax/libs/immutable/3.7.6/immutable.js"></script>
-        <script src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.34/browser.js"></script>
+        <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.0.1/react.min.js"></script>
+        <script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.0.1/react-dom.min.js"></script>
+        <script src="https://cdnjs.cloudflare.com/ajax/libs/immutable/3.7.6/immutable.min.js"></script>
+        <script src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.34/browser.min.js"></script>
         <script src="lib/Draft.js"></script>
         <script type="text/javascript" src="//use.typekit.net/vqa1hcx.js"></script>
         <script type="text/javascript">{'try{Typekit.load();}catch(e){}'}</script>

website/static/css/custom.css

@@ -151,4 +151,26 @@ pre code.hljs.css {
 .docMainWrapper .mainContainer .wrapper .post h5,
 .docMainWrapper .mainContainer .wrapper .post h6 {
   font-weight: bold;
-}
+}
+
+@media screen and (max-width: 767px) {
+  .hide-on-mobile {
+    display: none;
+  }
+  
+  .home-getting-started {
+    width: 100%;
+  }
+
+  .buttons-unit {
+    margin: 30px 0 60px;
+  }
+
+  .hero .text,
+  .hero .minitext,
+  .buttons-unit,
+  .home-getting-started {
+    box-sizing: border-box;
+    padding: 0 15px;
+  }
+}