docs: update release notes

docs/release-notes/release-notes-0.15.0.md

@@ -5,6 +5,11 @@
 * [Misconfigured ZMQ
   setup now gets reported](https://github.com/lightningnetwork/lnd/pull/5710).
 
+## `lncli`
+
+* Add [auto-generated command-line completions](https://github.com/lightningnetwork/lnd/pull/4177) 
+  for Fish shell.  
+
 ## Misc
 
 * [An example systemd service file](https://github.com/lightningnetwork/lnd/pull/6033)
@@ -20,4 +25,5 @@
 # Contributors (Alphabetical Order)
 
 * Daniel McNally
-* ErikEk
+* ErikEk
+* Torkel Rogstad