docs: release-notes-0.21.0

Author: MPins

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

@@ -44,6 +44,10 @@
 # Technical and Architectural Updates
 ## BOLT Spec Updates
 
+LND now [fail BOLT-11 payments](https://github.com/lightning/bolts/pull/1243)
+if any mandatory field (`p`, `h`, `s`, `n`) does not have the correct length
+(52, 52, 52, 53) in the BOLT 11 invoice.
+
 ## Testing
 
 ## Database
@@ -53,3 +57,5 @@
 ## Tooling and Documentation
 
 # Contributors (Alphabetical Order)
+
+Pins