Add pending release notes for accepting dual-funded channels

Author: dunxen

pending_changelog/3137-accept-dual-funding-without-contributing.txt

@@ -0,0 +1,15 @@
+# API Updates
+ * Accepting dual-funded (V2 establishment) channels (without contibuting) is now supported (#3137).
+   Some particulars to be aware of for this feature:
+   * Creating dual-funded channels is not yet supported.
+   * Contributing funds (inputs) to accepted channels is not yet supported.
+   * `Event::OpenChannelRequest::push_msat` has been replaced by the field `channel_negotiation_type` to
+     differentiate between an inbound request for a dual-funded (V2) or non-dual-funded (V1) channel to be
+     opened, with value being either of the enum variants `InboundChannelFunds::DualFunded` and
+     `InboundChannelFunds::PushMsat(u64)` corresponding to V2 and V1 channel open requests respectively.
+   * If `manually_accept_inbound_channels` is false, then V2 channels will be accepted automatically; the
+     same behaviour as V1 channels. Otherwise, `ChannelManager::accept_inbound_channel()` can also be used
+     to manually accept an inbound V2 channel.
+   * 0conf dual-funded channels are not supported.
+   * RBF of dual-funded channel funding transactions is not supported.
+