document custom favicon

doc/administration/index.md

@@ -58,6 +58,7 @@ Learn how to install, configure, update, and maintain your GitLab instance.
 #### Customizing GitLab's appearance
 
 - [Header logo](../customization/branded_page_and_email_header.md): Change the logo on all pages and email headers.
+- [Favicon](../customization/favicon.md): Change the default favicon to your own logo.
 - [Branded login page](../customization/branded_login_page.md): Customize the login page with your own logo, title, and description.
 - [Welcome message](../customization/welcome_message.md): Add a custom welcome message to the sign-in page.
 - ["New Project" page](../customization/new_project_page.md): Customize the text to be displayed on the page that opens whenever your users create a new project.

doc/customization/favicon.md

+# Changing the favicon
+
+> [Introduced][ce-14497] in GitLab 11.0.
+
+[ce-14497]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/14497
+
+Navigate to the **Admin** area and go to the **Appearance** page.
+
+Upload the custom favicon (**Favicon**) in the section **Favicon**.
+
+![appearance](favicon/appearance.png)
+
+After saving the page, the new favicon will be shown in the browser. The main
+favicon as well as the CI status icons will show the custom icon:
+
+![custom_favicon](favicon/custom_favicon.png)