Simplify copy on "Create a new list" dropdown in Issue Boards

## What does this MR do?

It changes the "Create new list" text to simply "Add list". It also describes the operation in a more concise way. It was suggested in #24659.

## Are there points in the code the reviewer needs to double check?

Although I refactored references to the name of the button to reflect the new text, I left part of the documentation unmodified:

File: `doc/user/project/issue_board.md`
```
In short, here's a list of actions you can take in an Issue Board:                 
                                                                                   
- [Create a new list](#creating-a-new-list).                                       
- [Delete an existing list](#deleting-a-list). 
```
because I was not sure if changing those was necessary.


Additionally, I replaced every occurrence of `click_button 'Create new list'` with `click_button 'Add list'`in the spec. I'm not sure if that causes any change in behavior as I am not sure if there are any hooks to the previous name, explicitly.

File: `spec/features/boards/boards_spec.rb`

## Why was this MR needed?

It is an improvement, as suggested in #24659

## Screenshots (if relevant)

**Before:**
![before](/uploads/cffd30b0e9a21d16bc25d046eb4ca42b/before.png)

**After:**
![after2](/uploads/95b049e0c1c565c4ccd1a72a3f4be925/after2.png)

## Does this MR meet the acceptance criteria?

- [X] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [X] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [X] All builds are passing
- [X] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [X] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [X] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [X] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
#24659

See merge request !7605

Move abuse report spinach test to RSpec

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

See merge request !7659

Remove heading ids from University docs

Having ids in headings was preventing the ToC to render correctly

See merge request !7720

[ci skip]

Fix `LFS enabled` select box.

A refactor of the project edit page caused the `lfs_enabled` setting to be reverted to a non functioning state. This MR fixes that.

This will most likely need to be ported back to 8.13 and 8.14. 8.12 contained the correct code.

Fixes #24645 

Related commits:

- ea3bbbde
- da07c2e4

cc @stanhu @dblessing @dbalexandre @rymai

See merge request !7716

Use Commit#author so we share logic and cache

See merge request !7715

It was not displaying the proper value and had an out of place look to it.

Closes #24900

move timeago.js to vendor directory

## What does this MR do?

moves timeago.js into `/vendor/assets/javascripts` for consistency with other external javascript libraries.

## Are there points in the code the reviewer needs to double check?

make sure timeago still works as it should...?  I don't see how this could have broken anything.

## Why was this MR needed?

consistency with our guidelines

## Does this MR meet the acceptance criteria?

- Tests
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

See discussion in [!6274](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/6274#note_18625583)

See merge request !7590

fixes non-retina shadow and browser zoom issue

## What does this MR do?
This MR closes #24851 and shadow issue for browser zoom 

## Are there points in the code the reviewer needs to double check?
NR

## Screenshots (if relevant)
**Ratina Display:**
![normal](/uploads/18fb0e321eff55cb89413745413cfe8a/normal.png)

**Non Retina**
![non-retina](/uploads/85ce8d3b22a025c251142bebe30c4401/non-retina.png)

**110% zoom**
![ratina](/uploads/bc0f2468ba780998e0e2b60a6d07e8db/ratina.png)

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [x] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?


Closes #24851

See merge request !7712

Use default `closest` if available!

## What does this MR do?

We should use the default `Element.prototype.closest` if its available.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

See merge request !7706

Fixed dragging issues on issue boards

## What does this MR do?

This fixes a few issues all at once:

- Fixes an issue when dragging an issue to a list but actually removes another issue from the original list
- Fixes an issue that caused the issue card to be appended to the bottom of the list
- Fixes an issue when dragging an issue would actually open up the sidebar

## What are the relevant issue numbers?

Closes #24654

See merge request !7701

Adds polyfill for CustomEvent

## What does this MR do?
CustomEvent is not supported by IE.- https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent

In order to stop using jQuery in new files that need to listen to custom events we need this polyfill.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

See merge request !7705

Fix BASH usage in the .gitlab-ci.yml

As discussed on Slack. Even though I created the fix, I was a mere code monkey in this case.

See merge request !7693

API: Add endpoint to delete a group share

Closes #24771

See merge request !7662

add details that Git LFS must be enabled in project

## What does this MR do?

Add details that Git LFS must be enabled in project before it will work

See merge request !7680

Grapify the sidekiq metrics API

Related to #22928

See merge request !7699

part of https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

Add support of Chrome/Chromium in requirements.md

See merge request !7703

[ci skip]

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/24863

See merge request !7698

Closes #24654

Add a starting date to milestones

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/23704

See merge request !7484

post_receive: accept any user email from last commit

See merge request !7225

Use authorized projects in ProjectTeam

Closes #23938 and #23636

See merge request !7586

Ensure we sanitize branch names with path-unfriendly characters

See merge request !7696

Closes #23938