f add docs

Author: TheBlueMatt

lightning/src/ln/channel.rs

@@ -429,6 +429,8 @@ pub(super) struct Channel<Signer: Sign> {
 	last_sent_closing_fee: Option<(u64, Signature)>, // (fee, holder_sig)
 	target_closing_feerate_sats_per_1000_weight: Option<u32>,
 
+	/// The minimum and maximum absolute fee we are willing to place on the closing transaction.
+	/// These are set once we reach `closing_negotiation_ready`.
 	#[cfg(test)]
 	pub(crate) closing_fee_limits: Option<(u64, u64)>,
 	#[cfg(not(test))]