Add copy paste text for closing down the Github issue tracker

@sytses I think we talked about closing down the Issue tracker on Github. A first step can be closing all the older issues and steering people towards the gitlab.com issue tracker.

What do you think about this text?

See merge request !1689

Use issue editor as cross reference comment author when issue is edited with a new mention.

Fixes #3244.

See merge request !1696

Bump nprogress-rails to 0.1.6.7

Closes #2866

See merge request !1686

Remove deprecated CI events from project settings page
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

cc @ayufan 

Part of #2594 

See merge request !1694

Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Fixed the permission doc

The guest users was missing "Pull project code" and "Download project".

/cc @axil 

See merge request !1695

The guest users was missing "Pull project code" and "Download project".

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Bump gitlab-shell to v2.6.6



See merge request !1673

Bump jquery-atwho-rails to ~> 1.3.2

Closes #2858

See merge request !1687

Add projects path index

Fixes performance regression introduced by !1649

See merge request !1692

Add builds to the docs  as a valid skip option for backups.



See merge request !1666

Fixes performance regression introduced by MR1649

Fix: 500 error returned if destroy request without HTTP referer

[ci skip]

Fix CI badge

The previous code relied on having on ref stored in commit, however the ref was moved to the build.

Fixes #3104

See merge request !1690

Fix visibility of specific runners

See merge request !1688

The previous code relied on having on ref stored in commit, however the ref was moved to the build.

Add migration to remove the contents of the satellites dir

See merge request !1681

Closes #2858

Closes #2866

Fix some grammatical issues

Ci status for merge requests index page

![ci-mr-index](/uploads/1424564c87ac6ff5fb2c4bc260fbebdf/ci-mr-index.png)


See merge request !1682

[ci skip]

Add missing character

This adds the missing character `a` to the help-text

Added missing period in gitlab_flow article.

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>