Added app switcher (#297)

Author: juskora

docs/getting_started/discover_ui.md

@@ -14,15 +14,20 @@ Depending on your location within the Back Office, it can contain the following
 - Global search field that allows you to [find content](../search/search_for_content.md) by checking all searchable Fields
 - Drop-down that changes the site context
 - Notification icon that informs you about incoming assignments, for example, items assigned for [your review](../content_management/workflow_management/editorial_workflow.md#review-queue)
+- App switcher which includes links to official websites of the QNTM group ecosystem companies, world-class ad-tech and mar-tech solution providers
 - User avatar with a drop-down menu with access to [user profile and settings](get_started.md#view-and-edit-user-profile)
 
+![Top bar](img/top_bar_all.png "Top bar")
+
 !!! note "Site context"
 
     Changing the site context results in the [Content Tree](#content-tree) showing content items that belong to the selected website.
     The appearance of content items can also change if they use different designs or languages depending on the [SiteAccess](../website_organization/multisite.md#siteaccess) settings.
 
 ![Top bar with site context selector](img/top_bar.png "Top bar with site context selector")
 
+![App switcher](img/app_switcher.png "App switcher")
+
 ## Dashboard
 
 The first screen that you see after logging in is [Dashboard](dashboard.md).