Add access-control-allow-origin http header to COS Gerrit

BUG=b/239224440

Change-Id: I1b952beaa1e1bf6c2a075a571e90e05e2bad5302
Reviewed-on: https://cos-review.googlesource.com/c/cos/tools/+/35787
Reviewed-by: Arnav Kansal <rnv@google.com>
Tested-by: Emmanuel Ketsri <emmank@google.com>
Cloud-Build: Arnav Kansal <rnv@google.com>
diff --git a/src/cmd/changelog-webapp/app.yaml b/src/cmd/changelog-webapp/app.yaml
index 818ff25..672dd64 100644
--- a/src/cmd/changelog-webapp/app.yaml
+++ b/src/cmd/changelog-webapp/app.yaml
@@ -34,3 +34,8 @@
   COS_FINDBUILD_TABLE_NAME: "cos-findbuild-table-name"
   COS_FINDBUILD_PASSWORD_NAME: "cos-findbuild-password-name"
   COS_FINDBUILD_INSTANCE_NAME: "cos-findbuild-instance-name"
+
+handlers:
+- url: /findreleasedbuild
+  http_headers:
+    Access-Control-Allow-Origin: https://cos-review.googlesource.com