Added shortcut to help shortcuts view

Updated shortcuts.png for docs

Updated CHANGELOG

Moved CHANGELOG entry

updated shortcut docs

CHANGELOG

@@ -72,6 +72,7 @@ v 8.9.0 (unreleased)
   - Projects pending deletion will render a 404 page
   - Measure queue duration between gitlab-workhorse and Rails
   - Added Gfm autocomplete for labels
+  - Added edit note 'up' shortcut documentation to the help panel and docs screenshot #18114
   - Make Omniauth providers specs to not modify global configuration
   - Remove unused JiraIssue class and replace references with ExternalIssue. !4659 (Ilan Shamir)
   - Make authentication service for Container Registry to be compatible with < Docker 1.11

app/views/help/_shortcuts.html.haml

@@ -28,8 +28,12 @@
                     .key ⌘ shift p
                   - else
                     .key ctrl shift p
-
                 %td Toggle Markdown preview
+              %tr
+                %td.shortcut
+                  .key
+                    %i.fa.fa-arrow-up
+                %td Edit last comment (when focused on an empty textarea)
             %tbody
               %tr
                 %th