Merge branch 'js-i18n-vue-shared' into 'master'

Internationalisation of vue_shared directory

See merge request gitlab-org/gitlab-ce!27751

app/assets/javascripts/vue_shared/components/content_viewer/lib/viewer_utils.js

+import { __ } from '~/locale';
+
 const viewers = {
   image: {
     id: 'image',
   },
   markdown: {
     id: 'markdown',
-    previewTitle: 'Preview Markdown',
+    previewTitle: __('Preview Markdown'),
   },
 };
 

locale/gitlab.pot

@@ -6688,6 +6688,9 @@ msgstr ""
 msgid "Preview"
 msgstr ""
 
+msgid "Preview Markdown"
+msgstr ""
+
 msgid "Preview changes"
 msgstr ""