* add a system_font_ui setting on the server

* Plug the system_font_ui on the front-end

* add EN/FR locales for the new setting

* put Roboto after all other fonts

* remove trailing whitespace so CodeClimate is happy

* fix user_spec.rb

* correctly write user_spect this time

* slightly better way of adding the classes

* add comments to the system-font stack for clarification

* use .system-font for the class instead

* don't use multiple lines for comments

* remove trailing whitespace

* use the classnames module for consistency

* use `mastodon-font-sans-serif` instead of Roboto directly

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.

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

* 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 2ddea9a6c8.

* fix: Issues mentions in the PR feedback

* Replace TextIconButton for SensitiveButton to IconButton

* line-height

* Bring Toot button in line with counter

Both should use stringz I guess

* Use grapheme_length for character count

* Debounce autosuggestions

* Remove duplicate import

* Unread indicator was invisible behind column header, adjusted

* Unread indicator now a CSS pseudo-element

* Adjust flex

* Re-add clear notifications button

* remove connect() in column_settings

* one line

* remove unused props

* Move ancestors/descendants out of timelines reducer

* Refactor timelines reducer

All types of timelines now have a flat structure and use the same
reducer functions and actions

* Reintroduce some missing behaviours

* Fix wrong import in reports

* Fix includes typo

* Fix issue related to "next" pagination in timelines and notifications

* Fix bug with timeline's initial state, expandNotifications

before the full-size image is loaded

* 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

* Add support key shortcut to Onboarding Modal

* this.state.pages -> this.pages

* 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

Focus the submit button when boost modal is opened.

* Remove react-imageloader

* add eslint-disable-line

* improve image loading experience

* remove unneeded import

* use PureComponent

* Use componentWillMount instead of constructor

* Set delete_modal preference to true by default
* Does not show confirmation modal if delete_modal is false
* Add ja translation for preference setting page