docs: add release notes.

Signed-off-by: Nishant Bansal <nishant.bansal.282003@gmail.com>

Author: NishantBansal2003

docs/release-notes/release-notes-0.19.0.md

@@ -94,6 +94,10 @@
   are now [sorted](https://github.com/lightningnetwork/lnd/pull/9337) based on
   the `InvoiceHTLC.HtlcIndex`.
 
+* [routerrpc.SendPaymentV2](https://github.com/lightningnetwork/lnd/pull/9359)
+  RPC method now applies a default timeout of 60 seconds when the
+  `timeout_seconds` field is not set or is explicitly set to 0.
+
 ## lncli Additions
 
 * [A pre-generated macaroon root key can now be specified in `lncli create` and