f add decay example

Author: TheBlueMatt

lightning/src/routing/scoring.rs

@@ -414,7 +414,11 @@ pub struct ProbabilisticScoringParameters {
 	/// the available liquidity is halved and the upper-bound moves half-way to the channel's total
 	/// capacity.
 	///
-	/// Default value: 1 hour
+	/// For example, if the channel's capacity is 1 million sats, and the current upper- and lower-
+	/// liquidity bounds are 200,000 sats and 600,000 sats, after this amount of time the upper-
+	/// and lower- liquidity bounds will be decayed to 100,000 and 800,000 sats.
+	///
+	/// Default value:  hour
 	///
 	/// # Note
 	///