Merge "Add Documentation menu entry for Project Owner Guide" into stable-2.9

Documentation/intro-project-owner.txt

diff --git a/Documentation/intro-project-owner.txt b/Documentation/intro-project-owner.txt
index 84f482b..64df285 100644
--- a/Documentation/intro-project-owner.txt
+++ b/Documentation/intro-project-owner.txt
@@ -547,6 +547,18 @@
 are inherited by the child projects. A child project can overwrite an
 inherited download command, or remove it by assigning no value to it.
 
+[[theme]]
+== Theme
+
+Gerrit supports project-specific themes for customizing the appearance
+of the change screen and the diff screens. It is possible to define an
+HTML header and footer and to adapt Gerrit's CSS. Details about themes
+are explained in the link:config-themes.html[Themes] section.
+
+Project-specific themes can only be installed by Gerrit administrators
+since the theme files must be copied into the Gerrit installation
+folder.
+
 [[tool-integration]]
 == Integration with other tools