Merge branch 'eslint' into 'master'

Add ESLint

## What does this MR do?

- create `package.json`
- add ESLint dependencies to `package.json`
- add JavaScript linting to CI
- add Rake task `lint:javascript`as alias for `eslint` (which itself is an alias for `npm run eslint`)

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

Probably not.

## Why was this MR needed?

My hovercraft was full of eels.

## What are the relevant issue numbers?

- https://gitlab.com/gitlab-org/gitlab-ce/issues/13224#note_12537431
- https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5006#note_13255658


See merge request !5445

.eslintignore

+/public/
+/tmp/
+/vendor/
+

.eslintrc

+{
+  "extends": "airbnb",
+  "globals": {
+    "$": false,
+    "_": false,
+    "beforeEach": false,
+    "d3": false,
+    "define": false,
+    "describe": false,
+    "document": false,
+    "expect": false,
+    "fixture": false,
+    "gl": false,
+    "it": false,
+    "jQuery": false,
+    "Mousetrap": false,
+    "spyOn": false,
+    "spyOnEvent": false,
+    "Turbolinks": false,
+    "window": false
+  }
+}
+

.gitignore

@@ -37,6 +37,7 @@
 /doc/code/*
 /dump.rdb
 /log/*.log*
+/node_modules/
 /nohup.out
 /public/assets/
 /public/uploads.*

.gitlab-ci.yml

@@ -311,6 +311,14 @@ coverage:
     - coverage/index.html
     - coverage/assets/
+lint-javascript:
+  stage: test
+  image: "node:latest"
+  before_script:
+    - npm install
+  script:
+    - npm run eslint
+
 # Trigger docs build
 # https://gitlab.com/gitlab-com/doc-gitlab-com/blob/master/README.md#deployment-process
 trigger_docs:

app/assets/javascripts/abuse_reports.js.es6

+/* eslint-disable */
 ((global) => {
   const MAX_MESSAGE_LENGTH = 500;
   const MESSAGE_CELL_SELECTOR = '.abuse-reports .message';

app/assets/javascripts/activities.js

+/* eslint-disable */
 (function() {
   this.Activities = (function() {
     function Activities() {

app/assets/javascripts/admin.js

+/* eslint-disable */
 (function() {
   this.Admin = (function() {
     function Admin() {

app/assets/javascripts/api.js

+/* eslint-disable */
 (function() {
   this.Api = {
     groupsPath: "/api/:version/groups.json",

app/assets/javascripts/application.js

+/* eslint-disable */
 // This is a manifest file that'll be compiled into including all the files listed below.
 // Add new JavaScript/Coffee code in separate files in this directory and they'll automatically
 // be included in the compiled file accessible from http://example.com/assets/application.js

app/assets/javascripts/aside.js

+/* eslint-disable */
 (function() {
   this.Aside = (function() {
     function Aside() {

app/assets/javascripts/autosave.js

+/* eslint-disable */
 (function() {
   this.Autosave = (function() {
     function Autosave(field, key) {

app/assets/javascripts/awards_handler.js

+/* eslint-disable */
 (function() {
   this.AwardsHandler = (function() {
     const FROM_SENTENCE_REGEX = /(?:, and | and |, )/; //For separating lists produced by ruby's Array#toSentence

app/assets/javascripts/behaviors/autosize.js

+/* eslint-disable */
 /*= require jquery.ba-resize */
 /*= require autosize */

app/assets/javascripts/behaviors/details_behavior.js

+/* eslint-disable */
 (function() {
   $(function() {
     $("body").on("click", ".js-details-target", function() {

app/assets/javascripts/behaviors/quick_submit.js

+/* eslint-disable */
 // Quick Submit behavior
 //
 // When a child field of a form with a `js-quick-submit` class receives a

app/assets/javascripts/behaviors/requires_input.js

+/* eslint-disable */
 // Requires Input behavior
 //
 // When called on a form with input fields with the `required` attribute, the

app/assets/javascripts/behaviors/toggler_behavior.js

+/* eslint-disable */
 (function(w) {
   $(function() {
     // Toggle button. Show/hide content inside parent container.

app/assets/javascripts/blob/blob_ci_yaml.js.es6

+/* eslint-disable */
 /*= require blob/template_selector */
 ((global) => {

app/assets/javascripts/blob/blob_file_dropzone.js

+/* eslint-disable */
 (function() {
   this.BlobFileDropzone = (function() {
     function BlobFileDropzone(form, method) {

app/assets/javascripts/blob/blob_gitignore_selector.js

+/* eslint-disable */
 /*= require blob/template_selector */