f - Add id_to_peer lock order docs

Author: ViktorTigerstrom

lightning/src/ln/channelmanager.rs

@@ -762,6 +762,8 @@ pub struct ChannelManager<Signer: Sign, M: Deref, T: Deref, K: Deref, F: Deref,
 	/// We should add `counterparty_node_id`s to `MonitorEvent`s, and eventually rely on it in the
 	/// future. That would make this map redundant, as only the `ChannelManager::per_peer_state` is
 	/// required to access the channel with the `counterparty_node_id`.
+	///
+	/// Locked *after* `channel_state`.
 	id_to_peer: Mutex<HashMap<[u8; 32], PublicKey>>,
 
 	our_network_key: SecretKey,