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>

./bin/tootctl media remove --days 7 --background

Make the old rake task point to it

* Port travis_retry for CI

* Add license

* Update better_errors to version 2.4.0

* Update binding_of_caller to version 0.7.3

* Update bootsnap to version 1.1.5

* Update browser to version 2.5.2

* Update capistrano to version 3.10.0

* Update capistrano-bundler to version 1.3.0

* Update capistrano-rbenv to version 2.1.2

* Update capybara to version 2.15.4

* Update cld3 to version 3.2.1

* Update fabrication to version 2.18.0

* Update fog-openstack to version 0.1.22

* Update kaminari to version 1.1.1

* Update lograge to version 0.7.1

* Update nokogiri to version 1.8.1

* Update oj to version 3.3.9

* Update ox to version 2.8.1

* Update parallel_tests to version 2.17.0

* Update pkg-config to version 1.2.8

* Update rspec-rails to version 3.7.1

* Update rubocop to version 0.51.0

* Update scss_lint to version 0.55.0

* Update sidekiq to version 5.0.5

* Update sidekiq-scheduler to version 2.1.10

* Update tzinfo-data to version 1.2017.3

* Update webpacker to version 3.0.2

* bundle update

* Fix webpack-dev-server on Windows

* Serve webpack from 0.0.0.0, access at 127.0.0.1

* 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

Previously the `bin/setup` script only installed the Ruby dependencies
via Bundler. This is not sufficient to get the test suite to pass. We
also need the JavaScript dependencies.

This commit installs the JavaScript dependencies as part of the
`bin/setup` script via Yarn.

This allows for a successful

    bin/setup && bundle exec rake

on a fresh clone of the repo.