docs: update release notes

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

@@ -65,6 +65,11 @@
 * [Properly handle un-acked updates for exhausted watchtower 
   sessions](https://github.com/lightningnetwork/lnd/pull/8233)
 
+* [Allow `shutdown`s while HTLCs are in-flight](https://github.com/lightningnetwork/lnd/pull/8167).
+  This change fixes an issue where we would force-close channels when receiving
+  a `shutdown` message if there were currently HTLCs on the channel. After this
+  change, the shutdown procedure should be compliant with BOLT2 requirements.
+
 # New Features
 ## Functional Enhancements
 
@@ -123,6 +128,12 @@
   file](https://github.com/lightningnetwork/lnd/pull/8188). The corresponding
   `lncli getdebuginfo` command was also added.
 
+* Add a [new flag](https://github.com/lightningnetwork/lnd/pull/8167) to the
+  `CloseChannel` RPC method that instructs the client to not wait for the
+  closing transaction to be negotiated. This should be used if you don't care
+  about the txid and don't want the calling code to block while the channel
+  drains the active HTLCs.
+
 ## lncli Additions
 
 * Deprecate `bumpclosefee` for `bumpforceclosefee` to accommodate for the fact 

peer/brontide.go

@@ -3636,12 +3636,13 @@ func (p *Brontide) handleCloseMsg(msg *closeMsg) {
 		oShutdown.WhenSome(func(msg lnwire.Shutdown) {
 			// if the link is nil it means we can immediately queue
 			// the Shutdown message since we don't have to wait for
-			// commitment transaction synchronization
+			// commitment transaction synchronization.
 			if link == nil {
 				p.queueMsg(typed, nil)
 				return
 			}
-			// When we have a Shutdown to send, we defer it til the
+
+			// When we have a Shutdown to send, we defer it till the
 			// next time we send a CommitSig to remain spec
 			// compliant.
 			link.OnCommitOnce(htlcswitch.Outgoing, func() {