Add 3.3 whatsnew to index.
diff --git a/Doc/whatsnew/index.rst b/Doc/whatsnew/index.rst
index 8220bd2..c60818a 100644
--- a/Doc/whatsnew/index.rst
+++ b/Doc/whatsnew/index.rst
@@ -11,6 +11,7 @@
 .. toctree::
    :maxdepth: 2
 
+   3.3.rst
    3.2.rst
    3.1.rst
    3.0.rst