Merge branch '19157-use-shortcuts-is-not-working-on-gitlab-com-help' into 'master'

Fixed 'use shortcuts' button on docs

## What does this MR do?

Exposes 'onToggleHelp() to window object through `showHelp()` so a help panel can be toggled globally using `showHelp()`.

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

Is this the best implementation? I actually think this is tidier than doing something like `onclick="new Shortcuts().onToggleHelp"` or `$.trigger 'keydown', char: '?'` but let me know.

## Why was this MR needed?

Docs UX

## What are the relevant issue numbers?

Closes #19157.

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry 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 [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)
Closes #19157

See merge request !4979

app/assets/javascripts/shortcuts.js.coffee

@@ -9,12 +9,12 @@ class @Shortcuts
 
   onToggleHelp: (e) =>
     e.preventDefault()
-    @toggleHelp(@enabledHelp)
+    Shortcuts.toggleHelp(@enabledHelp)
 
-  toggleMarkdownPreview: (e) =>
+  toggleMarkdownPreview: (e) ->
     $(document).triggerHandler('markdown-preview:toggle', [e])
 
-  toggleHelp: (location) ->
+  @toggleHelp: (location) ->
     $modal = $('#modal-shortcuts')
 
     if $modal.length

app/views/help/index.html.haml

@@ -36,6 +36,6 @@
       %ul.well-list
         %li= link_to 'See our website for getting help', promo_url + '/getting-help/'
         %li= link_to 'Use the search bar on the top of this page', '#', onclick: 'Shortcuts.focusSearch(event)'
-        %li= link_to 'Use shortcuts', '#', onclick: 'Shortcuts.showHelp(event)'
+        %li= link_to 'Use shortcuts', '#', onclick: 'Shortcuts.toggleHelp()'
         %li= link_to 'Get a support subscription', 'https://about.gitlab.com/pricing/'
         %li= link_to 'Compare GitLab editions', 'https://about.gitlab.com/features/#compare'