Add index link to the 2.2.2 ReleaseNotes

Change-Id: I8beaf212cbf425f5dfb1b90d96c6d03548986c2b
diff --git a/ReleaseNotes/index.txt b/ReleaseNotes/index.txt
index 2039222..b6dd4b2 100644
--- a/ReleaseNotes/index.txt
+++ b/ReleaseNotes/index.txt
@@ -4,6 +4,7 @@
 [[2_2]]
 Version 2.2.x
 -------------
+* link:ReleaseNotes-2.2.2.html[2.2.2],
 * link:ReleaseNotes-2.2.1.html[2.2.1],
 * link:ReleaseNotes-2.2.0.html[2.2.0]