docs+build: Prepare release of version 0.4.0

Change-Id: Ibd3129da74afa24a35115789a517e562f0a12639
Refs: #3178
diff --git a/docs/index.rst b/docs/index.rst
index 94157be..e75dec9 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -18,6 +18,13 @@
    FAQ
    manpages
 
+.. toctree::
+   :hidden:
+   :maxdepth: 1
+
+   RELEASE_NOTES
+   releases
+
 * :doc:`overview`
 
   A brief overview of NFD and its major modules.
@@ -49,7 +56,9 @@
 
 * `API Documentation (doxygen) <doxygen/annotated.html>`_
 
-* `Release Notes <RELEASE_NOTES.html>`_
+* :doc:`RELEASE_NOTES`
+
+* :doc:`releases`
 
 License
 -------