doc: add v1.22-rc1 release notes

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
diff --git a/doc/release-notes/index.rst b/doc/release-notes/index.rst
index b06ec9d..8a2e32d 100644
--- a/doc/release-notes/index.rst
+++ b/doc/release-notes/index.rst
@@ -11,4 +11,4 @@
    v1.21
    v1.21.1
    v1.21.2
-
+   v1.22-rc1