f - add reference to Serialization Compatibility section

Author: jkczyz

CHANGELOG.md

@@ -8,7 +8,7 @@
    will be on by default in the future (#1351).
  * `OpenChannelRequest` now has a `channel_type` field indicating the features
    the channel will operate with and should be used to filter channels with
-   undesirable features (#1351).
+   undesirable features (#1351). See the Serialization Compatibility section.
  * `ChannelManager` supports sending and receiving short channel id aliases in
    the `funding_locked` message. These are used when forwarding payments and
    constructing invoice route hints for improved privacy. `ChannelDetails` has a