* feat: Lazy-load routes

* feat: Lazy-load modals

* feat: Lazy-load columns

* refactor: Simplify Bundle API

* feat: Optimize bundles

* feat: Prevent flashing the waiting state

* feat: Preload commonly used bundles

* feat: Lazy load Compose reducers

* feat: Lazy load Notifications reducer

* refactor: Move all dynamic imports into one file

* fix: Minor bugs

* fix: Manually hydrate the lazy-loaded reducers

* refactor: Move all dynamic imports to async-components

* fix: Loading modal style

* refactor: Avoid converting the raw state for each lazy hydration

* refactor: Remove unused component

* refactor: Maintain modal name

* fix: Add as=script to preload link

* chore: Fix lint error

* fix(components/bundle): Check if timestamp is set when computing elapsed

* fix: Load compose reducers for the onboarding modal

* Update links in status content on update as well as mount
Fixes occasional bugs with mentions and hashtags not being set to open in a new column like they should, and instead opening in a new page

* use classList instead of raw className

This fixes a warning on status unmounting (e.g. deletion).

This also resets IntersectionObserverWrapper on disconnect to avoid `unobserve()` calls
which has bug in Edge.

* feat(components/media_gallery): Responsive images

* fix(components/media_gallery): Link to image URL

* Remove unused column_collapsable.js
* Remove old styles
* Extract `> div`  style to independent class

ref https://tc39.github.io/proposal-decorators/

(This patch has been merged as bugfix and reverted, but still valuable as
improvement)

Previously, we've attached IntersectionObserver twice for boosted statuses:
wrapper Status and wrapped Status. but wrapped Status don't need to manage
intersection and visibility by itself, because it's a part of wrapper Status.

* Revert "Bump version to 1.4.4"

This reverts commit 1585b0c6.

* Revert "Fix conversations (fixes #3869) (#3870)"

This reverts commit 15b43f55.

* Revert "Fix streaming server. Redis connection subscribe for each channel. (#3828)"

This reverts commit d8ec8328.

* Revert "Filter direct statuses in Status.as_home_timeline (#3842)"

This reverts commit bab5a182.

* Revert "Fix RemoteFollow behavior (#3868)"

This reverts commit a20cf3b6.

* Revert "Update fabricator for MediaAttachment to attach a file according to type (#3862)"

This reverts commit 356df7ae.

* Revert "Upgrade React Router (#3677)"

This reverts commit 8f03fdce.

* Revert "Do not call setState from unmounted component (#3853)"

This reverts commit 1fc6cb49.

* Revert "Replace TextIconButton for SensitiveButton to IconButton (#3759)"

This reverts commit eb832e88.

* Revert "Fix RTL detection on Ruby side (#3867)"

This reverts commit b16b6935.

* Revert "i18n: Fixed typo in Polish translation (#3864)"

This reverts commit da6fa029.

* Revert "Don't attach IntersectionObserver for wrapped statuses (#3863)"

This reverts commit 94ad0706.

* chore(yarn): Remove react-router

* chore(yarn): Remove react-router-scroll

* chore(yarn): Remove history

* chore(yarn): Add react-router-dom

* chore: Remove usages of react-router-scroll

* refactor: Upgrade to react-router-web

* refactor: Use fork of react-router-scroll

This reverts commit 2ddea9a6c8d39fc64b7d0b587f3fbda7a45a7fa2.

* fix: Issues mentions in the PR feedback

Stop an executing task if the component already unmounted.

This fixes a bug that sometimes boosted statuses being hidden on scrolling.

Previously, we've attached IntersectionObserver twice for boosted statuses:
wrapper Status and wrapped Status. This will call intersection handler twice,
so this may results race condition...probably.

* Unread indicator was invisible behind column header, adjusted

* Unread indicator now a CSS pseudo-element

* Adjust flex

- Use plaintext
- Strip out URLs
- Strip out mentions
- Strip out hashtags
- Strip out whitespace from "overall" count
- Consistent between JS and Ruby

* Add regex filter on the community timeline and the public timeline

* correcting

* Adjust the height of header buttons

* Remove trailing spaces

* Remove trailing spaces

* Solve some code duplication

* reset the state of the locale files in app/javascript/mastodon/locales

* adjust to upstream

* adjust to upstream

* change keys of locale settings

* Add react/no-string-refs ESLint rule

* Add react/jsx-boolean-value ESLint rule

* Add react/jsx-closing-bracket-location ESLint rule

* Add react/jsx-indent ESLint rule

* Add react/jsx-curly-spacing ESLint rule

* Add react/jsx-equals-spacing ESLint rule

* Add react/jsx-first-prop-new-line ESLint rule

* Add react/jsx-no-duplicate-props ESLint rule

* Add react/jsx-tag-spacing ESLint rule

* Add quotes ESLint rule

* Add jsx-quotes ESlint rule

* Sort ESLint rules

* Allow mounting arbitrary columns

* Refactor column headers, allow pinning/unpinning and moving columns around

* Collapse animation

* Re-introduce scroll to top

* Save column settings properly, do not display pin options in
single-column view, do not display collapse icon if there is
nothing to collapse

* Fix one instance of public timeline being closed closing the stream
Fix back buttons inconsistently sending you back to / even if history exists

* Getting started displays links to columns that are not mounted

* Change PureComponent to ImmutablePureComponent

Change PureComponent to ImmutablePureComponent in AttachmentList.

* rm React.