docs: update release notes

docs/release-notes/release-notes-0.18.4.md

@@ -24,9 +24,52 @@
   does not contain a payment address.
 
 # New Features
+
+The main channel state machine and database now allow for processing and storing
+custom Taproot script leaves, [allowing the implementation of custom channel
+types](https://github.com/lightningnetwork/lnd/pull/8960).
+
 ## Functional Enhancements
+
+* A new `protocol.simple-taproot-overlay-chans` configuration item/CLI flag was
+  added [to turn on custom channel
+  functionality](https://github.com/lightningnetwork/lnd/pull/8960).
+
 ## RPC Additions
 
+* Some new experimental [RPCs for managing SCID
+  aliases](https://github.com/lightningnetwork/lnd/pull/8960) were added under
+  the `routerrpc` package. These methods allow manually adding and deleting SCID
+  aliases locally to your node.
+  > NOTE: these new RPC methods are marked as experimental
+  (`XAddLocalChanAliases` & `XDeleteLocalChanAliases`) and upon calling
+  them the aliases will not be communicated with the channel peer.
+
+* The responses for the `ListChannels`, `PendingChannels` and `ChannelBalance`
+  RPCs now include [a new `custom_channel_data` field that is only set for 
+  custom channels](https://github.com/lightningnetwork/lnd/pull/8960).
+
+* The `routerrpc.SendPaymentV2` RPC has a new field [`first_hop_custom_records`
+  that allows the user to send custom p2p wire message TLV types to the first
+  hop of a payment](https://github.com/lightningnetwork/lnd/pull/8960).
+  That new field is also exposed in the `routerrpc.HtlcInterceptor`, so it can
+  be read and interpreted by external software.
+
+* The `routerrpc.HtlcInterceptor` now [allows some values of the HTLC to be
+  modified before they're validated by the state
+  machine](https://github.com/lightningnetwork/lnd/pull/8960). The fields that
+  can be modified are `outgoing_amount_msat` (if transported overlaid value of
+  HTLC doesn't match the actual BTC amount being transferred) and
+  `outgoing_htlc_wire_custom_records` (allow adding custom TLV values to the
+  p2p wire message of the forwarded HTLC).
+
+* A new [`invoicesrpc.HtlcModifier` RPC now allows incoming HTLCs that attempt
+  to satisfy an invoice to be modified before they're
+  validated](https://github.com/lightningnetwork/lnd/pull/8960). This allows
+  custom channels to determine what the actual (overlaid) value of an HTLC is,
+  even if that value doesn't match the actual BTC amount being transferred by
+  the HTLC.
+
 ## lncli Additions
 
 # Improvements
@@ -36,6 +79,7 @@
 
 ## lncli Updates
 
+
 ## Code Health
 
 ## Breaking Changes
@@ -54,3 +98,8 @@
 # Contributors (Alphabetical Order)
 
 * Elle Mouton
+* ffranr
+* George Tsagkarelis
+* Olaoluwa Osuntokun
+* Oliver Gugger
+