Document that serving project documentation must be enabled

Change-Id: I1dd5dc473073ce560bc8e67c5083752f94a3db46
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
diff --git a/src/main/resources/Documentation/about.md b/src/main/resources/Documentation/about.md
index 0ef6a46..93b3846 100644
--- a/src/main/resources/Documentation/about.md
+++ b/src/main/resources/Documentation/about.md
@@ -20,6 +20,8 @@
 * [Create Reference](../../../Documentation/access-control.html#category_create)
   to enable users to upload images.
 
-In addition the image mime types must be
+In addition Gerrit must be
+[configured to serve project documentation from Markdown](../../../Documentation/config-gerrit.html#site.enableSrcToMarkdown)
+to make images available for browsing. Also the image mime types must be
 [configured as safe](../../../Documentation/config-gerrit.html#mimetype.name.safe)
 because otherwise Gerrit refuses to render the images.