Add prelude to mark the first release as part of Kolla

Change-Id: Ie8cad275089315ef62b826ff3ab720537bc71cdb

releasenotes/notes/first-official-release-6dff5747d34d161c.yaml

+---
+prelude: >
+    This Kayobe release is the first as part of an official OpenStack project.
+    Kayobe is now a deliverable of the `Kolla project
+    <https://governance.openstack.org/tc/reference/projects/kolla.html>`_.