Cleans up and refreshes generated website resources (#1998)

Summary:
**Summary**

Cleans up unused website resources from before the migration to Docusaurus, and makes sure static website resources are generated and refreshed at every build.

**Test Plan**

```
yarn
cd website
yarn build
yarn start
```

Website loads and pages contain the expected content.
Pull Request resolved: facebookarchive/draft-js#1998

Reviewed By: niveditc

Differential Revision: D14004275

Pulled By: niveditc

fbshipit-source-id: 2d0afaf448ae5d1c6f9f6915e530c50c983135d1

Author: aforismesen

.gitignore

@@ -7,3 +7,4 @@ website/src/docs/
 npm-debug.log
 !website/static/
 yarn-error.log
+.DS_Store

gulpfile.js

@@ -38,6 +38,7 @@ var paths = {
     '!src/**/__mocks__/**/*.js',
   ],
   css: ['src/**/*.css'],
+  static: 'website/static',
 };
 
 var babelOptsJS = {
@@ -242,6 +243,22 @@ gulp.task(
   }),
 );
 
+gulp.task(
+  'website:static',
+  gulp.series('dist:min', 'css',
+    gulp.parallel(function() {
+      return gulp
+        .src(paths.dist + '/Draft.min.js')
+        .pipe(gulp.dest(paths.static + '/lib'));
+    }),
+    gulp.parallel(function() {
+      return gulp
+        .src(paths.dist + '/Draft.css')
+        .pipe(gulp.dest(paths.static + '/css'));
+    }),
+  )
+);
+
 gulp.task(
   'check-dependencies',
   gulp.series(function() {
@@ -269,6 +286,6 @@ gulp.task(
     'check-dependencies',
     'clean',
     gulp.parallel('modules', 'flow'),
-    gulp.parallel('dist', 'dist:min'),
+    gulp.parallel('dist', 'dist:min', 'website:static'),
   ),
 );

meta/bundle-size-stats/Draft.js.json

@@ -272,7 +272,7 @@ class Index extends React.Component {
         <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 src="lib/Draft.min.js"></script>
         <script type="text/javascript" src="//use.typekit.net/vqa1hcx.js"></script>
         <script type="text/javascript">{'try{Typekit.load();}catch(e){}'}</script>
         <script type="text/babel" dangerouslySetInnerHTML={{__html: richExample}} />