https://github.com/webpack/webpack-dev-server/issues/762

Sketch 43 files are technically a zip file, so the JavaScript opens the
zip file & locates a preview.png which is just a quick preview of the
last sketch page edited. After that is loaded it simply places the image
into the DOM

 - gl_emoji for falling back to image/css-sprite when the browser
   doesn't support an emoji
 - Markdown rendering (Banzai filter)
 - Autocomplete
 - Award emoji menu
    - Perceived perf
    - Immediate response because we now build client-side
 - Update `digests.json` generation in gemojione rake task to be more
   useful and  include `unicodeVersion`

MR: !9437

See issues

 - #26371
 - #27250
 - #22474

jQuery UI is no longer used anywhere so say goodbye to it from package.json & Gemfile

see: https://docs.npmjs.com/misc/semver

See https://github.com/stefanpenner/es6-promise/issues/100

```
[WDS] Warnings while compiling.
./vendor/assets/javascripts/es6-promise.auto.js
Module not found: Error: Can't resolve 'vertx' in
'/Users/eric/Documents/gitlab/gitlab-development-kit/gitlab/vendor/assets/javascripts'
 @ ./vendor/assets/javascripts/es6-promise.auto.js 140:16-26
 @ ./app/assets/javascripts/application.js
 @ multi (webpack)-dev-server/client?http://localhost:3808
./application.js
```

This reverts merge request !9044

Part of #18437 to remove jQuery UI. This removes the datepicker