f improve internal docs on FundingSpendConfirmation

Author: TheBlueMatt

lightning/src/chain/channelmonitor.rs

@@ -394,8 +394,12 @@ enum OnchainEvent {
 	MaturingOutput {
 		descriptor: SpendableOutputDescriptor,
 	},
+	/// A spend of the funding output, either a commitment transaction or a cooperative closing
+	/// transaction.
 	FundingSpendConfirmation {
 		txid: Txid,
+		/// The CSV delay for the output of the funding spend transaction (implying it is a local
+		/// commitment transaction, and this is the delay on the to_self output).
 		on_local_output_csv: Option<u16>,
 	},
 }