CHANGELOG-3.4: add sha256sum

Signed-off-by: Sam Batschelet <sbatsche@redhat.com>

CHANGELOG-3.4.md

@@ -594,6 +594,8 @@ Note: **v3.5 will deprecate `etcd --log-package-levels` flag for `capnslog`**; `
 
 - Add [`etcd-dump-logs --entry-type`](https://github.com/etcd-io/etcd/pull/9628) flag to support WAL log filtering by entry type.
 - Add [`etcd-dump-logs --stream-decoder`](https://github.com/etcd-io/etcd/pull/9790) flag to support custom decoder.
+- Add [`SHA256SUM`](https://github.com/etcd-io/etcd/pull/11087) file to release assets.
+  - etcd maintainers are a distributed team, this change allows for releases to be cut and validation provided without requiring a signing key.
 
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