Add release notes page for version 22.1.0

Tempest 22.1.0 has been released in Train but releasenote
page was not added for that.

Change-Id: I899d18ee33bd2b94d81f65b62a2b32f643a2d262
diff --git a/releasenotes/source/index.rst b/releasenotes/source/index.rst
index 43c102c..611979d 100644
--- a/releasenotes/source/index.rst
+++ b/releasenotes/source/index.rst
@@ -6,6 +6,7 @@
    :maxdepth: 1
 
    unreleased
+   v22.1.0
    v22.0.0
    v21.0.0
    v20.0.0