docs: update release notes

docs/release-notes/release-notes-0.18.0.md

@@ -220,6 +220,10 @@
 * Allow `healthcheck` package users to provide [custom callbacks](https://github.com/lightningnetwork/lnd/pull/8504)
   which will execute whenever a healthcheck succeeds/fails.
 
+* `PublishTransaction` now [returns the error
+  types](https://github.com/lightningnetwork/lnd/pull/8554) defined in
+  `btcd/rpcclient`.
+
 ### Logging
 * [Add the htlc amount](https://github.com/lightningnetwork/lnd/pull/8156) to
   contract court logs in case of timed-out htlcs in order to easily spot dust