Create releasenotes page for tempest 37.0.0, 38.0.0

Depends-On: https://review.opendev.org/c/openstack/releases/+/913952
Change-Id: I0840bbeafb3a2398998ccf199cab04067cb74b0c
diff --git a/releasenotes/source/v38.0.0.rst b/releasenotes/source/v38.0.0.rst
new file mode 100644
index 0000000..2664374
--- /dev/null
+++ b/releasenotes/source/v38.0.0.rst
@@ -0,0 +1,6 @@
+=====================
+v38.0.0 Release Notes
+=====================
+
+.. release-notes:: 38.0.0 Release Notes
+   :version: 38.0.0