Add release notes

Closes-Bug: CLOUDOPS-761
Change-Id: If1aa57c0e1617a312f36e52c503a40b5ee166c91
(cherry picked from commit 7607e5a65486453e80b1a7a042051df61e672301)
diff --git a/releasenotes/config.yaml b/releasenotes/config.yaml
new file mode 100644
index 0000000..e2c8d6c
--- /dev/null
+++ b/releasenotes/config.yaml
@@ -0,0 +1 @@
+default_branch: main