docs: release-notes-0.21.0

Author: MPins

docs/release-notes/release-notes-0.21.0.md

@@ -303,6 +303,9 @@
 # Technical and Architectural Updates
 ## BOLT Spec Updates
 
+LND now [enforces](https://github.com/lightning/bolts/pull/1284) low-S canonical
+signatures when `n` field is present in a BOLT11 invoice.
+
 ## Testing
 
 * [Added unit tests for TLV length validation across multiple packages](https://github.com/lightningnetwork/lnd/pull/10249).
@@ -435,3 +438,4 @@
 * Pins
 * Suheb
 * Ziggie
+* Pins