docs: Add a shortcut to Developer Setup

Finding this doc has been a barrier to entry for some as it explains the
basics of how to setup a Gerrit development environment and test site.

Change-Id: Ib9719cbb6b70acffb73b656a5fce7f764d9e5990
Release-Notes: documentation improvements
diff --git a/Documentation/index.txt b/Documentation/index.txt
index 9afd6e3..c3d79b1 100644
--- a/Documentation/index.txt
+++ b/Documentation/index.txt
@@ -15,6 +15,7 @@
 == Contributor Guides
 . link:dev-community.html[Gerrit Community]
 . link:dev-community.html#how-to-contribute[How to Contribute]
+.. link:dev-readme.html[Developer Setup]
 
 == User Guides
 . link:intro-user.html[User Guide]