Bumps [webpacker](https://github.com/rails/webpacker) from 3.5.5 to 4.0.2.
- [Release notes](https://github.com/rails/webpacker/releases)
- [Changelog](https://github.com/rails/webpacker/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rails/webpacker/compare/v3.5.5...v4.0.2)

Signed-off-by: dependabot[bot] <support@dependabot.com>
Co-authored-by: Yamagishi Kazutoshi <ykzts@desire.sh>

Fix #6856
Fix #6951

* Revert "Fix some icon names changed by the Font Awesome 5. (#8796)"

This reverts commit 3f9ec3de82.

* Revert "Migrate to font-awesome 5.0. (#8799)"

This reverts commit 8bae14591b.

* Revert "Fix some icons names, unavailable in fontawesome5 (free license). (#8792)"

This reverts commit b9c727a945.

* Revert "Update the icon name changed by the Font Awesome 5. (#8776)"

This reverts commit 17af4d27da.

* Revert "Add bot icon to bot avatars and migrate to newer version of Font Awesome (#8484)"

This reverts commit 4b794e134d.

* Verify link ownership with rel="me"

* Add explanation about verification to UI

* Perform link verifications

* Add click-to-copy widget for verification HTML

* Redesign edit profile page

* Redesign forms

* Improve responsive design of settings pages

* Restore landing page sign-up form

* Fix typo

* Support <link> tags, add spec

* Fix links not being verified on first discovery and passive updates

* add several missing alt tags

* remove alt text from mascot images

Follow-up to #8142

Follow-up to #6124

- Add missing meta description to profiles
- Add canonical rel link to landing page
- Remove linebreaks from title tags
- Add username to profile title
- Add toots/following/followers to profile description tags
- Add next/prev rel links to profiles
- Do not index follower/following variants of profiles

* Improve styling of closed registrations message, rename button

"Sign up on another server"

Fix #6683

* Adjust styling of closed registrations message

* Use grid layout for the landing page

* Fix column settings

Set the ratio explicitly

* Improve information board

* Redesign landing page (again)

* Move login form in small version to the right column

* Display closed registrations message

* Add site setting for the hero image

* Fix test

* Increase spacing, maximum width, change call to action section

They were redundant, and also had a inconsistency; the button for
"other instances" had an icon for the external link in "more" page, but
it didn't in the other pages.

This unifies the implementation, and the external link icon is now shown
in all the about pages.

* Adjust landing pages 2

Fix styles of terms page
Remove action buttons from timeline in about page
Adjust styles of short description
Adjust form inputs
Set autocomplete off for username and email box in registration form. Remove line breakings.

* Revert removing action buttons

* Improve OpenGraph tags for about pages

* Add thumbnail admin setting

* Fix error

* Fix up

* Add Mastodon::Source.url

* Update spec

* Refactor

Move things frmo Mastodon::Source to Mastodon::Version

apply same style class to the About description on both the landing page
and the about/more page

Empty a element is created when there is no business e-mail input.

* Set contact address as mailto link

To be able to copy long email address

* Set style for mailto link

* Fix autocomplete in two_factor.html.haml

* Fix autocomplete in registrations edit.html.haml

* Fix autocomplete in passwords edit.html.haml

* Fix autocomplete in _registration.html.haml

* Fix autocomplete in new.html.haml

* Fix autocomplete in show.html.haml

* Add autocomplete option to sessions new.html.haml

* Add autocomplete option to 2FA new.html.haml

* Add autocomplete option to 2FA show.html.haml

* Redesign /terms page

* Fix tests

* Remove unused keys

* Redesign extended information page

* Remove unused keys

* Add $ui-base-lighter-color variable to SCSS

* Add new logo

* Remove unused images

* Redesign the landing page, mount public timeline on it

* Adjust the standalone mounted component to the lacking of router

* Adjust auth layout pages to new design

* Fix tests

* Standalone public timeline polling every 5 seconds

* Remove now obsolete translations

* Add responsive design for new landing page

* Address reviews

* Add floating clouds behind frontpage form

* Use access token from public page when available

* Fix mentions and hashtags links, cursor on status content in standalone mode

* Add footer link to source code

* Fix errors on pages that don't embed the component, use classnames

* Fix tests

* Change anonymous autoPlayGif default to false

* When gif autoplay is disabled, hover to play

* Add option to hide the timeline preview

* Slightly improve alt layout

* Add elephant friend to new frontpage

* Display "back to mastodon" in place of "login" when logged in on frontpage

* Change polling time to 3s

* add haml_lint to Gemfile

* add .haml-lint.yml

* fix warnings of haml_lint

* Added japanese version of terms of service and privacy policy

* Fix typo

* Add trasnlation for title.

* Improve translation and update the date.

* Replace browserify with webpack

* Add react-intl-translations-manager

* Do not minify in development, add offline-plugin for ServiceWorker background cache updates

* Adjust tests and dependencies

* Fix production deployments

* Fix tests

* More optimizations

* Improve travis cache for npm stuff

* Re-run travis

* Add back support for custom.scss as before

* Remove offline-plugin and babili

* Fix issue with Immutable.List().unshift(...values) not working as expected

* Make travis load schema instead of running all migrations in sequence

* Fix missing React import in WarningContainer. Optimize rendering performance by using ImmutablePureComponent instead of
React.PureComponent. ImmutablePureComponent uses Immutable.is() to compare props. Replace dynamic callback bindings in
<UI />

* Add react definitions to places that use JSX

* Add Procfile.dev for running rails, webpack and streaming API at the same time

* add og:url to stream_item view

* add og:url and text to about/show

* add og:url to profile, followers and follows pages