CHANGELOG: highlight "snapshot" package and godoc link

Signed-off-by: Gyuho Lee <gyuhox@gmail.com>

CHANGELOG-3.4.md

@@ -134,6 +134,7 @@ See [security doc](https://github.com/coreos/etcd/blob/master/Documentation/op-g
 ### Added: API
 
 - Add [`snapshot`](https://github.com/coreos/etcd/pull/9118) package for snapshot restore/save operations.
+  - See [`godoc.org:etcd/snapshot`](https://godoc.org/github.com/coreos/etcd/snapshot).
 - Add [`watch_id` field to `etcdserverpb.WatchCreateRequest`](https://github.com/coreos/etcd/pull/9065), allow user-provided watch ID to `mvcc`.
   - Corresponding `watch_id` is returned via `etcdserverpb.WatchResponse`, if any.
 - Add [`raftAppliedIndex` field to `etcdserverpb.StatusResponse`](https://github.com/coreos/etcd/pull/9176) for current Raft applied index.

CHANGELOG-4.0.md

@@ -9,7 +9,7 @@ See [code changes](https://github.com/coreos/etcd/compare/v3.3.0...v4.0.0) and [
 
 ### Breaking Changes
 
-- [Secure etcd by default](https://github.com/coreos/etcd/issues/9475).
+- [Secure etcd by default](https://github.com/coreos/etcd/issues/9475)?
 - Change `/health` endpoint output.
   - Previously, `{"health":"true"}`.
   - Now, `{"health":true}`.