Fix #7659

* Revert "Do not re-position scroll when loading more (inserting items from below) (#7344)"

This reverts commit 8c601b54.

* Revert "Prevent timeline from moving when cursor is hovering over it (fixes #7278) (#7327)"

This reverts commit 58852695.

* Update React.JS

* Use React's new lifecycles for scrollable lists

* Clean up dead code

* Make CodeClimate happy

onScrollToBottom was a function to run instead of onScrollToTop and
onScroll when scrolling to the bottom. The behavior to prevent
onScrollToTop was inconvenient because the viewport can be at the bottom
and at the top at the same time if the viewport is larger than the
container.

onScrollToBottom was also called when the button to load more is clicked
on contray to the name suggests, which led notifications and
status_list_container components to mark the scrolled location is not at
the top mistakenly.

onLoadMore is a replacement for onScrollToBottom. It will be called
independently from onScrollToTop and onScroll.

* Fix #2102 - Implement hotkeys

Hotkeys on status list:

- r to reply
- m to mention author
- f to favourite
- b to boost
- enter to open status
- p to open author's profile
- up or k to move up in the list
- down or j to move down in the list
- 1-9 to focus a status in one of the columns
- n to focus the compose textarea
- alt+n to start a brand new toot
- backspace to navigate back

* Add navigational hotkeys

The key g followed by:

- s: start
- h: home
- n: notifications
- l: local timeline
- t: federated timeline
- f: favourites
- u: own profile
- p: pinned toots
- b: blocked users
- m: muted users

* Add hotkey for focusing search, make escape un-focus compose/search

* Fix focusing notifications column, fix hotkeys in compose textarea

* Toggle contain:strict on fullscreen

* Fix scss lint issue

* fix scss whitespace lint issue

* Fix behavior while the button is invisible
e.g. pointer cursor, couldn't open contextmenu
* Avoid rendering the button to remove blank space if no more items are available or no items are rendered

It wasn't working ideally and introduced some annoying false positivies

Resolved:

* Lot of redundant renders while mouse moving
* Scroll jumping when timeline loaded
* Scroll position isn't kept when statuses below the scrollTop was deleted then new status arrived

Unresolved:

* Scroll position isn't kept when statuses over the scrollTop was deleted then new status arrived
-> It needs to know which statuses are over the scrollTop
* New status indicator should be active when new statuses arrived while mouse moved recently
-> It needs a) update indicator in ScrollableList, or b) set scrollTop status while mouse moving

* fix(modal_root): Read type from props, not from component

* fix(status_list): Do not user event.path

* fix(status): Add tabIndex=0

* fix(status_list): Make keyboard navigable

* fix(dropdown_menu): Keyboard navigation

* fix(icon_button): Add aria-pressed attribute

* fix(privacy_dropdown): Make accessible

* fix(emoji_picker_dropdown): Make accessible

* fix(icon_button): Support tabIndex

* fix(actions_modal): Remove icon from tab order

* fix(dropdown_menu): Add role=group

* fix(setting_toggle): Toggle via space key

* fix(dropdown_menu): Remove redundant handling of Space key

* fix(emoji_picker_dropdown): Remove redundant Space key handling

* fix(privacy_dropdown): Remove redundant Space key handling

* fix(status): Switch to article and add aria-posinset, aria-setsize

* fix(status_list): Use role=feed and pass more ARIA props to Status

* chore(eslint): jsx-a11y/role-supports-aria-props

* fix(components/media_modal): Center horizontally in Firefox

* fix(components/status_list): Do not remove load more button

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

* Unread indicator was invisible behind column header, adjusted

* Unread indicator now a CSS pseudo-element

* Adjust flex

* refactor(components/status_list): Lazy load using IntersectionObserver

* refactor(components/status_list): Avoid setState bottleneck

* refactor(components/status_list): Update state correctly

* fix(components/status): Render if isIntersecting is undefined

* refactor(components/status): Recycle timeout

* refactor(components/status): Reduce animation duration

* refactor(components/status): Use requestIdleCallback

* chore: Split polyfill bundles

* refactor(components/status_list): Increase rootMargin to 300%

* fix(components/status): Check if onRef is not defined

* chore: Add note about polyfill bundle splitting

* fix(components/status): Reduce animation duration to 0.3 seconds

original: https://github.com/tootsuite/mastodon/pull/2618

* Add semi to ESLint rules

* Add padded-blocks to ESLint rules

* Add comma-dangle to ESLint rules

* add config/webpack and storyboard

* add streaming/

* yarn test:lint -- --fix

* refactor(components/status_list): Avoid quering scrollTop if not necessary

* refactor(components/dropdown_menu): Do not render items if not expanded

* refactor: Cherry-pick react-motion imports

* refactor(compose/privacy_dropdown): Do not render options if not open

* refactor(components/column_collapsable): Do not render children if collapsed

Use ES Class Fields & Static Properties (currently stage 2) for improve class outlook.

Added babel-plugin-transform-class-properties as a Babel plugin.

* 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