Merge branch 'mjang-add-GDK-for-rake' into 'master'

Add tip that rake requires GDK

See merge request gitlab-org/gitlab!42280

doc/development/i18n/externalization.md

@@ -7,6 +7,9 @@ For working with internationalization (i18n),
 used tool for this task and there are a lot of applications that will help us to
 work with it.
 
+TIP: **Tip:**
+All `rake` commands described on this page must be run on a GitLab instance, usually GDK.
+
 ## Setting up GitLab Development Kit (GDK)
 
 In order to be able to work on the [GitLab Community Edition](https://gitlab.com/gitlab-org/gitlab-foss)