Fill in the devguide index page

BUG=None
R=sbc@chromium.org

Review URL: https://codereview.chromium.org/23999002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@221739 0039d316-1c4b-4281-b951-d872f2087c98

native_client_sdk/src/doc/devguide/index.rst

@@ -4,5 +4,12 @@
 Developer's Guide
 #################
 
-This is the index of the ``devguide`` directory.
+The Native Client Developer's Guide includes practical information you need to
+get your development cycle up and running (e.g., how to compile and test-run
+your application), as well as important concepts you need to understand in order
+to code your application (e.g., how an application is structured, and how to use
+the Pepper APIs).
 
+The Developer's Guide is a work-in-progress. Please send feedback to the
+`native-client-discuss group
+<https://groups.google.com/group/native-client-discuss>`_.