Add `/assign me` alias support for assigning issuables to oneself

Closes #35304

See merge request !13334

Remove unused #tree-holder

Closes #36035

See merge request !13338

Currently, when a user wants to assign an issue/MR to himself, he needs
to type his full username or select it from the suggested ones in the
dropdown list.
This commits suggest a faster solution which is typing `/assign me`

Closes #35304.

Add a missing whitespace in "private forks you have no access to"

Closes #35786

See merge request !13332

Add custom linter for inline JavaScript to haml_lint

See merge request !9742

Add 9.5 update guide, with Gitaly specifics

Closes gitaly#416

See merge request !13309

Expose more attributes to unauthenticated GET /projects/:id

See merge request !13283

Synchronous zanata community contribution translation

See merge request !13266

Add Korean translation to i18n

Closes #35852

See merge request !13243

Upgrade haml_lint Gem to 0.26.0

See merge request !13304

Fix Mattermost integration

See merge request !13305

Update the guides for updating GitLab and adding background migrations

See merge request !13284

Gitaly deletions and annotations

See merge request !13280

Merge Request widget Improvements

Closes #33095

See merge request !12601

Fix issues with pdf-js dependencies

See merge request !13328

Fix #35786

Fix order of CI lint ace editor loading

Closes #35985

See merge request !13316

Fix Timezone Inconsistencies in User Contribution Calendar

Closes #27616 and #1943

See merge request !13208

Add missing CHANGELOG.md entries for security release on 2017-01-23

See merge request !13327

Fix "Cannot connect to CI server error messages"

Closes #34547

See merge request !13252

Fix "pipeline_schedules pages throwing error 500" when "Active Ci::PipelineSchedule have a nullified `next_run_at`"

Closes #32790

See merge request !13286

Update top bar issues icon

Closes #35275

See merge request !13263

Fix pipeline icon in contextual nav for projects

See merge request !13324

34060 Simply general project settings to use expanded panels

Closes #34060

See merge request !12620

Since mysql is not a priority anymore, test it less

See merge request !13320

Install 'yarn' globally to avoid PATH issues

See merge request !13273

Make dividers of new dropdown style full width

Closes #35784

See merge request !13276